0001140361-22-003916 | S-1 | XBRL Viewer

As of December 31,

Dimension Energy LLC

Carrying value

Ownership percentage

Print Document View Excel Document

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2021
Cover [Abstract]
Document Type	S-1
Amendment Flag	false
Entity Registrant Name	FTC Solar, Inc.
Entity Central Index Key	0001828161
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

Consolidated Balance Sheets (FY) - USD ($)	Sep. 30, 2021	Jun. 30, 2021	Apr. 05, 2021	Jan. 08, 2021	Dec. 31, 2020	Sep. 30, 2020	Jul. 21, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash	$ 140,662,000				$ 32,359,000					$ 7,221,000
Restricted cash	0				1,014,000					1,014,000
Accounts receivable, net	53,668,000				23,734,000					14,048,000
Inventories	11,276,000				1,686,000					4,505,000
Prepaid and other current assets	23,558,000				6,924,000					3,848,000
Total current assets	229,164,000				65,717,000					30,636,000
Intangible assets, net					0					33,000	$ 33,000
Investments in unconsolidated subsidiary	0				1,857,000					2,582,000
Other assets	6,265,000				3,819,000					579,000
Total assets	235,429,000				71,393,000					33,830,000
Current liabilities
Accounts payable	16,556,000				17,127,000					8,191,000
Line of credit	0				1,000,000					0
Accrued expenses and other liabilities	40,246,000				18,495,000					5,375,000
Accrued interest - related party	0				207,000					285,000
Deferred revenue	9,606,000				22,980,000					19,873,000
Total current liabilities	66,408,000				59,809,000					33,724,000
Long-term debt and other borrowings	0				784,000					1,976,000
Long-term debt - related party					0					5,857,000
Other non-current liabilities	5,662,000				3,349,000					715,000
Deferred income taxes					0					3,000
Total liabilities	72,070,000				63,942,000					42,275,000
Commitments and contingencies (Note 9)
Stockholders' equity (deficit)
Preferred stock	0				0
Common stock par value of $0.0001 per share, 98,960,064 shares authorized at December 31, 2020 and 2019; 66,155,340 and 63,633,981 shares issued and outstanding as of December 31, 2020 and 2019, respectively	8,000				1,000				$ 30,000,024	1,000
Treasury stock, at cost (9,896,666 and 0 shares as of December 31, 2020 and 2019, respectively)	0		$ 0	$ 0	0		$ 0			0
Additional paid-in capital	288,696,000				50,096,000					18,273,000
Accumulated other comprehensive loss	6,000				(3,000)					0
Accumulated deficit	(125,351,000)				(42,643,000)					(26,719,000)
Total stockholders' equity (deficit)	163,359,000	$ 180,772,000			7,451,000	$ 16,720,000		$ 19,124,000		(8,445,000)		$ (1,856,000)
Total liabilities and stockholders' equity (deficit)	$ 235,429,000				$ 71,393,000					$ 33,830,000

Consolidated Balance Sheets (FY) (Parenthetical) - $ / shares	Sep. 30, 2021	Apr. 28, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Stockholders' equity (deficit)
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001	$ 0.0001
Common stock, shares authorized	850,000,000		98,960,064		98,960,064	98,960,064
Common stock, shares issued	84,944,145		66,155,340	9,162,976	63,633,981
Common stock, shares outstanding	84,944,145		66,155,340		63,633,981
Treasury stock, shares	10,762,566		9,896,666		0

Consolidated Statements of Operations (FY) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
Consolidated Statements of Operations (FY) - USD ($)	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Total revenue	$ 52,989,000	$ 59,640,000			$ 168,804,000	$ 143,173,000	$ 187,352,000	$ 53,124,000
Cost of revenue:
Total cost of revenue	61,028,000	56,774,000			192,774,000	134,709,000	183,713,000	55,075,000
Gross profit (loss)	(8,039,000)	2,866,000			(23,970,000)	8,464,000	3,639,000	(1,951,000)
Operating expenses
Research and development	2,116,000	1,438,000			9,653,000	4,047,000	5,222,000	3,960,000
Selling and marketing	2,224,000	1,041,000			6,421,000	2,374,000	3,545,000	1,897,000
General and administrative	10,392,000	2,912,000			63,217,000	7,630,000	11,798,000	4,563,000
Total Operating expenses	14,732,000	5,391,000			79,291,000	14,051,000	20,565,000	10,420,000
Loss from operations	(22,771,000)	(2,525,000)			(103,261,000)	(5,587,000)	(16,926,000)	(12,371,000)
Interest expense, net	301,000	70,000			515,000	303,000	480,000	454,000
Gain from disposal in equity investment	210,000	0			20,829,000	0
Gain (loss) on extinguishment of debt	0	(34,000)			790,000	(75,000)	(116,000)	0
Other Nonoperating Expense	13,000	1,000			59,000	1,000
Total loss before income taxes	(22,875,000)	(2,630,000)			(82,216,000)	(5,966,000)	(17,406,000)	(12,825,000)
(Benefit from) income taxes	41,000	24,000			137,000	(115,000)	(83,000)	(39,000)
(Income) Loss from unconsolidated subsidiary	400	186,000			354,000	345,000	(1,399,000)	709,000
Net loss	$ (22,916,000)	$ (2,840,000)	$ (59,792,000)	$ (3,356,000)	$ (82,707,000)	$ (6,196,000)	$ (15,924,000)	$ (13,495,000)
Net loss per share
Basic	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Diluted	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Weighted-average common shares outstanding:
Basic	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Diluted	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Product
Revenue:
Total revenue	$ 45,582,000	$ 48,879,000			$ 137,799,000	$ 122,197,000	$ 158,925,000	$ 43,085,000
Cost of revenue:
Total cost of revenue	48,090,000	46,513,000			146,964,000	114,883,000	155,967,000	44,212,000
Service
Revenue:
Total revenue	7,407,000	10,761,000			31,005,000	20,976,000	28,427,000	10,039,000
Cost of revenue:
Total cost of revenue	$ 12,938,000	$ 10,261,000			$ 45,810,000	$ 19,826,000	$ 27,746,000	$ 10,863,000

Consolidated Statements of Comprehensive Loss (FY) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Comprehensive Loss [Abstract]
Net loss	$ (22,916)	$ (2,840)	$ (59,792)	$ (3,356)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Other comprehensive loss:
Foreign currency translation adjustments	3	(12)			9	(20)	(3)	0
Comprehensive loss	$ (22,913)	$ (2,852)			$ (82,698)	$ (6,216)	$ (15,927)	$ (13,495)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124452729-227067

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22658-107794

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669619-108580

Reference 25: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669625-108580

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

+ Details

Consolidated Statements of Stockholders' Equity (Deficit) (FY) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (1,856)	$ 1	$ 0	$ 11,367	$ 0	$ (13,224)
Beginning balance (in shares) at Dec. 31, 2018		56,146,407	0
Restricted stock awards vested during the period (in shares)		3,822,019
Issuance of common stock	6,000			6,000
Issuance of common stock (in shares)		3,665,555
Stock-based compensation	906			906
Net loss	(13,495)					(13,495)
Ending balance at Dec. 31, 2019	(8,445)	$ 1	$ 0	18,273	0	(26,719)
Ending balance (in shares) at Dec. 31, 2019		63,633,981	0
Restricted stock awards vested during the period (in shares)		2,014,091
Issuance of common stock	30,000			30,000
Issuance of common stock (in shares)		9,162,976
Stock-based compensation	933			933
Net loss	(3,356)					(3,356)
Other comprehensive loss	(8)				(8)
Ending balance at Jun. 30, 2020	19,124	$ 1	$ 0	49,206	(8)	(30,075)
Ending balance (in shares) at Jun. 30, 2020		74,811,048	0
Beginning balance at Dec. 31, 2019	(8,445)	$ 1	$ 0	18,273	0	(26,719)
Beginning balance (in shares) at Dec. 31, 2019		63,633,981	0
Net loss	(6,196)
Ending balance at Sep. 30, 2020	16,720	$ 1	$ 0	49,654	(20)	(32,915)
Ending balance (in shares) at Sep. 30, 2020		65,509,094	9,896,666
Beginning balance at Dec. 31, 2019	(8,445)	$ 1	$ 0	18,273	0	(26,719)
Beginning balance (in shares) at Dec. 31, 2019		63,633,981	0
Restricted stock awards vested during the period (in shares)		3,255,049
Issuance of common stock	30,000			30,000
Issuance of common stock (in shares)		9,162,976
Repurchase of common stock, held in treasury (in shares)		(9,896,666)	9,896,666
Stock-based compensation	1,823			1,823
Net loss	(15,924)					(15,924)
Other comprehensive loss	(3)				(3)
Ending balance at Dec. 31, 2020	7,451	$ 1	$ 0	50,096	(3)	(42,643)
Ending balance (in shares) at Dec. 31, 2020		66,155,340	9,896,666
Beginning balance at Jun. 30, 2020	19,124	$ 1	$ 0	49,206	(8)	(30,075)
Beginning balance (in shares) at Jun. 30, 2020		74,811,048	0
Restricted stock awards vested during the period (in shares)		594,712
Repurchase of common stock, held in treasury (in shares)		(9,896,666)	9,896,666
Stock-based compensation	448			448
Net loss	(2,840)					(2,840)
Other comprehensive loss	(12)				(12)
Ending balance at Sep. 30, 2020	16,720	$ 1	$ 0	49,654	(20)	(32,915)
Ending balance (in shares) at Sep. 30, 2020		65,509,094	9,896,666
Beginning balance at Dec. 31, 2020	7,451	$ 1	$ 0	50,096	(3)	(42,643)
Beginning balance (in shares) at Dec. 31, 2020		66,155,340	9,896,666
Restricted stock awards vested during the period (in shares)		3,413,849
Repurchase of common stock, held in treasury (in shares)		(865,900)	865,900
Stock-based compensation	53,150			53,150
Net loss	(59,792)					(59,792)
Other comprehensive loss	6				6
Ending balance at Jun. 30, 2021	180,772	$ 8		283,196	3	(102,435)
Ending balance (in shares) at Jun. 30, 2021		84,301,595	10,762,566
Beginning balance at Dec. 31, 2020	7,451	$ 1	$ 0	50,096	(3)	(42,643)
Beginning balance (in shares) at Dec. 31, 2020		66,155,340	9,896,666
Net loss	(82,707)
Ending balance at Sep. 30, 2021	163,359	$ 8		288,696	6	(125,351)
Ending balance (in shares) at Sep. 30, 2021		84,944,145	10,762,566
Beginning balance at Jun. 30, 2021	180,772	$ 8		283,196	3	(102,435)
Beginning balance (in shares) at Jun. 30, 2021		84,301,595	10,762,566
Stock-based compensation	5,381			5,381
Net loss	(22,916)					(22,916)
Other comprehensive loss	3				3
Ending balance at Sep. 30, 2021	$ 163,359	$ 8		$ 288,696	$ 6	$ (125,351)
Ending balance (in shares) at Sep. 30, 2021		84,944,145	10,762,566

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669619-108580

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442407-227067

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21463-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32136-110900

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=124507222&loc=d3e1436-108581

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442411-227067

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669625-108580

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=122038336&loc=d3e74512-122707

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Consolidated Statements of Cash Flows (FY) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Adjustments to reconcile net loss to cash (used in) provided by operating activities:
Stock-based compensation	58,531	1,381	1,818	906
Depreciation and amortization	383	43	47	412
(Income)/Loss from unconsolidated subsidiary, net of distributions received	354	345	(1,399)	709
Loss on debt extinguishment	(790)	75	116	0
Warranty provision	2,118	5,195	7,866	2,057
Gain from disposal of equity investment	(20,829)	0
Warranty asset	(484)	(726)
Warranty recoverable from manufacturers			(1,021)	(284)
Bad debt expense	83	0	24	444
Deferred income taxes	0	(2)	(3)	(3)
Other non-cash items	0	43	50	89
Changes in operating assets and liabilities:
Accounts receivable, net	(30,017)	(12,219)	(9,710)	(13,838)
Inventories	(9,590)	(1,523)	2,819	(4,505)
Prepaid and other current assets	(16,609)	(4,351)	(2,847)	(3,154)
Other assets	180	(365)	(1,672)	(156)
Accounts payable	(535)	4,009	8,936	7,781
Accruals and other current liabilities	21,243	13,825	7,162	3,389
Accrued interest - related party debt	(207)	(112)	(78)	(289)
Deferred revenue	(13,374)	(14,108)	3,107	19,683
Other non-current liabilities	904	386	496	1
Other, net	(1,068)	(338)	(298)	(1)
Net cash used in operating activities	(92,414)	(14,638)	(511)	(254)
Cash flows from investing activities:
Purchases of property and equipment	(778)	0	(256)	(18)
Proceeds from Sale of Equity Method Investments	22,332	0
Distributions received from unconsolidated subsidiary, return of investment			2,124	0
Net cash provided by (used in) investing activities:	21,554	0	1,868	(18)
Cash flows from financing activities:
Proceeds from borrowings	0	784	784	1,000
Repayments of borrowings	(1,000)	(4,000)	(7,000)	0
Repurchase and retirement of common stock	(54,155)	0
Offering cost paid	(5,942)	0
Deferred financing costs for revolving credit facility	(2,077)	0
Proceeds from stock issuance	241,314	30,000	30,000	6,000
Net cash provided by (used in) financing activities	178,140	26,784	23,784	7,000
Effect of exchange rate changes on cash and restricted cash	9	(20)	(3)	0
Net increase in cash and restricted cash	107,289	12,126	25,138	6,728
Cash and restricted cash at beginning of period	33,373	8,235	8,235	1,507
Cash and restricted cash at end of period	140,662	20,361	33,373	8,235
Supplemental disclosures of cash flow information:
Cash paid during the year for interest	332	350	350	708
Cash paid during the year for income taxes			0	0
Reconciliation of cash and restricted cash at period end
Cash	140,662	32,359	32,359	7,221
Restricted cash	0	1,014	1,014	1,014
Total cash and restricted cash	$ 140,662	$ 33,373	$ 33,373	$ 8,235

Condensed Consolidated Balance Sheets (Unaudited) (Q3) - USD ($)	Sep. 30, 2021	Jun. 30, 2021	Apr. 05, 2021	Jan. 08, 2021	Dec. 31, 2020	Sep. 30, 2020	Jul. 21, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash	$ 140,662,000				$ 32,359,000					$ 7,221,000
Restricted cash	0				1,014,000					1,014,000
Accounts receivable, net	53,668,000				23,734,000					14,048,000
Inventories	11,276,000				1,686,000					4,505,000
Prepaid and other current assets	23,558,000				6,924,000					3,848,000
Total current assets	229,164,000				65,717,000					30,636,000
Investments in unconsolidated subsidiary	0				1,857,000					2,582,000
Other assets	6,265,000				3,819,000					579,000
Total assets	235,429,000				71,393,000					33,830,000
Current liabilities
Accounts payable	16,556,000				17,127,000					8,191,000
Line of credit	0				1,000,000					0
Accrued expenses and other liabilities	40,246,000				18,495,000					5,375,000
Accrued interest - related party	0				207,000					285,000
Deferred revenue	9,606,000				22,980,000					19,873,000
Total current liabilities	66,408,000				59,809,000					33,724,000
Long-term debt and other borrowings	0				784,000					1,976,000
Long-term debt - related party					0					5,857,000
Other non-current liabilities	5,662,000				3,349,000					715,000
Deferred income taxes					0					(3,000)
Total liabilities	72,070,000				63,942,000					42,275,000
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock par value of $0.0001 per share, 10,000,000 shares authorized; none issued as of December 31, 2020 and September 30, 2021	0				0
Common stock par value of $0.0001 per share, 850,000,000 shares authorized; 66,155,340 and 84,944,145 shares issued and outstanding as of December 31, 2020 and September 30, 2021	8,000				1,000				$ 30,000,024	1,000
Treasury stock, at cost; 9,896,666 and 10,762,566 shares as of December 31, 2020 and September 30, 2021	0		$ 0	$ 0	0		$ 0			0
Additional paid-in capital	288,696,000				50,096,000					18,273,000
Accumulated other comprehensive income (loss)	6,000				(3,000)					0
Accumulated deficit	(125,351,000)				(42,643,000)					(26,719,000)
Total stockholders' equity (deficit)	163,359,000	$ 180,772,000			7,451,000	$ 16,720,000		$ 19,124,000		(8,445,000)	$ (1,856,000)
Total liabilities and stockholders' equity (deficit)	$ 235,429,000				$ 71,393,000					$ 33,830,000

Condensed Consolidated Balance Sheets (Q3) (Parenthetical) (Unaudited) - $ / shares	Sep. 30, 2021	Apr. 28, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	10,000,000		10,000,000
Preferred stock, shares issued	0		0
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001	$ 0.0001
Common stock, shares authorized	850,000,000		98,960,064		98,960,064	98,960,064
Common stock, shares issued	84,944,145		66,155,340	9,162,976	63,633,981
Common stock, shares outstanding	84,944,145		66,155,340		63,633,981
Treasury stock, shares	10,762,566		9,896,666		0

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (Q3) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Total revenue	$ 52,989,000	$ 59,640,000			$ 168,804,000	$ 143,173,000	$ 187,352,000	$ 53,124,000
Cost of revenue:
Total cost of revenue	61,028,000	56,774,000			192,774,000	134,709,000	183,713,000	55,075,000
Gross profit (loss)	(8,039,000)	2,866,000			(23,970,000)	8,464,000	3,639,000	(1,951,000)
Operating expenses
Research and development	2,116,000	1,438,000			9,653,000	4,047,000	5,222,000	3,960,000
Selling and marketing	2,224,000	1,041,000			6,421,000	2,374,000	3,545,000	1,897,000
General and administrative	10,392,000	2,912,000			63,217,000	7,630,000	11,798,000	4,563,000
Total Operating expenses	14,732,000	5,391,000			79,291,000	14,051,000	20,565,000	10,420,000
Loss from operations	(22,771,000)	(2,525,000)			(103,261,000)	(5,587,000)	(16,926,000)	(12,371,000)
Interest expense	(301,000)	(70,000)			(515,000)	(303,000)	(480,000)	(454,000)
Gain from disposal in equity investment	210,000	0			20,829,000	0
Gain (loss) on extinguishment of debt	0	(34,000)			790,000	(75,000)	(116,000)	0
Other Expense	(13,000)	(1,000)			(59,000)	(1,000)
Total loss before income taxes	(22,875,000)	(2,630,000)			(82,216,000)	(5,966,000)	(17,406,000)	(12,825,000)
(Expense) Benefit from income taxes	(41,000)	(24,000)			(137,000)	115,000	83,000	39,000
Loss from unconsolidated subsidiary	(400)	(186,000)			(354,000)	(345,000)	1,399,000	(709,000)
Net loss	(22,916,000)	(2,840,000)	$ (59,792,000)	$ (3,356,000)	(82,707,000)	(6,196,000)	(15,924,000)	(13,495,000)
Other comprehensive income (loss):
Foreign currency translation adjustments	3,000	(12,000)			9,000	(20,000)	(3,000)	0
Comprehensive loss	$ (22,913,000)	$ (2,852,000)			$ (82,698,000)	$ (6,216,000)	$ (15,927,000)	$ (13,495,000)
Net loss per share
Basic	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Diluted	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Weighted-average common shares outstanding:
Basic	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Diluted	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Product
Revenue:
Total revenue	$ 45,582,000	$ 48,879,000			$ 137,799,000	$ 122,197,000	$ 158,925,000	$ 43,085,000
Cost of revenue:
Total cost of revenue	48,090,000	46,513,000			146,964,000	114,883,000	155,967,000	44,212,000
Service
Revenue:
Total revenue	7,407,000	10,761,000			31,005,000	20,976,000	28,427,000	10,039,000
Cost of revenue:
Total cost of revenue	$ 12,938,000	$ 10,261,000			$ 45,810,000	$ 19,826,000	$ 27,746,000	$ 10,863,000

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) (Q3) - USD ($) $ in Thousands	Total	IPO [Member]	Common Stock	Common Stock IPO [Member]	Preferred Stock	Treasury Stock	Additional Paid-in Capital	Additional Paid-in Capital IPO [Member]	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (1,856)		$ 1			$ 0	$ 11,367		$ 0	$ (13,224)
Beginning balance (in shares) at Dec. 31, 2018			56,146,407			0
Restricted stock awards vested during the period (in shares)			3,822,019
Issuance of common stock	6,000						6,000
Issuance of common stock (in shares)			3,665,555
Stock-based compensation	906						906
Net Income (loss)	(13,495)									(13,495)
Ending balance at Dec. 31, 2019	(8,445)		$ 1		$ 0	$ 0	18,273		0	(26,719)
Ending balance (in shares) at Dec. 31, 2019			63,633,981		0	0
Restricted stock awards vested during the period (in shares)			2,014,091
Issuance of common stock	30,000						30,000
Issuance of common stock (in shares)			9,162,976
Stock-based compensation	933						933
Net Income (loss)	(3,356)									(3,356)
Other comprehensive income (loss)	(8)								(8)
Ending balance at Jun. 30, 2020	19,124		$ 1		$ 0	$ 0	49,206		(8)	(30,075)
Ending balance (in shares) at Jun. 30, 2020			74,811,048		0	0
Beginning balance at Dec. 31, 2019	(8,445)		$ 1		$ 0	$ 0	18,273		0	(26,719)
Beginning balance (in shares) at Dec. 31, 2019			63,633,981		0	0
Net Income (loss)	(6,196)
Ending balance at Sep. 30, 2020	16,720		$ 1		$ 0	$ 0	49,654		(20)	(32,915)
Ending balance (in shares) at Sep. 30, 2020			65,509,094		0	9,896,666
Beginning balance at Dec. 31, 2019	$ (8,445)		$ 1		$ 0	$ 0	18,273		0	(26,719)
Beginning balance (in shares) at Dec. 31, 2019			63,633,981		0	0
Restricted stock awards vested during the period (in shares)			3,255,049
Repurchase of treasury stock			(9,896,666)			9,896,666
Issuance of common stock upon exercise of stock options (in shares)	0
Issuance of common stock	$ 30,000						30,000
Issuance of common stock (in shares)			9,162,976
Stock-based compensation	1,823						1,823
Net Income (loss)	(15,924)									(15,924)
Other comprehensive income (loss)	(3)								(3)
Ending balance at Dec. 31, 2020	7,451		$ 1		$ 0	$ 0	50,096		(3)	(42,643)
Ending balance (in shares) at Dec. 31, 2020			66,155,340		0	9,896,666
Beginning balance at Jun. 30, 2020	19,124		$ 1		$ 0	$ 0	49,206		(8)	(30,075)
Beginning balance (in shares) at Jun. 30, 2020			74,811,048		0	0
Restricted stock awards vested during the period (in shares)			594,712
Repurchase of treasury stock			(9,896,666)			9,896,666
Stock-based compensation	448						448
Net Income (loss)	(2,840)									(2,840)
Other comprehensive income (loss)	(12)								(12)
Ending balance at Sep. 30, 2020	16,720		$ 1		$ 0	$ 0	49,654		(20)	(32,915)
Ending balance (in shares) at Sep. 30, 2020			65,509,094		0	9,896,666
Beginning balance at Dec. 31, 2020	7,451		$ 1		$ 0	$ 0	50,096		(3)	(42,643)
Beginning balance (in shares) at Dec. 31, 2020			66,155,340		0	9,896,666
Restricted stock awards vested during the period (in shares)			3,413,849
Repurchase of treasury stock			(865,900)			865,900
Issuance of common stock upon exercise of stock options	50						50
Issuance of common stock upon exercise of stock options (in shares)			213,690
Repurchase and retirement of common stock	(54,155)		$ (1)				(54,154)
Repurchase and retirement of common stock (shares)			(4,455,384)
Impact of Stock Split			$ 6				(6)
Deferred offering costs	(7,093)						(7,093)
Issuance of common stock		$ 241,155		$ 2				$ 241,153
Issuance of common stock (in shares)				19,840,000
Stock-based compensation	53,150						53,150
Net Income (loss)	(59,792)									(59,792)
Other comprehensive income (loss)	6								6
Ending balance at Jun. 30, 2021	180,772		$ 8		$ 0		283,196		3	(102,435)
Ending balance (in shares) at Jun. 30, 2021			84,301,595		0	10,762,566
Beginning balance at Dec. 31, 2020	7,451		$ 1		$ 0	$ 0	50,096		(3)	(42,643)
Beginning balance (in shares) at Dec. 31, 2020			66,155,340		0	9,896,666
Issuance of common stock (in shares)		4,455,384
Net Income (loss)	(82,707)
Ending balance at Sep. 30, 2021	163,359		$ 8		$ 0		288,696		6	(125,351)
Ending balance (in shares) at Sep. 30, 2021			84,944,145		0	10,762,566
Beginning balance at Jun. 30, 2021	180,772		$ 8		$ 0		283,196		3	(102,435)
Beginning balance (in shares) at Jun. 30, 2021			84,301,595		0	10,762,566
Issuance of common stock upon exercise of stock options	107						107
Issuance of common stock upon exercise of stock options (in shares)			642,550
Deferred offering costs	12						12
Stock-based compensation	5,381						5,381
Net Income (loss)	(22,916)									(22,916)
Other comprehensive income (loss)	3								3
Ending balance at Sep. 30, 2021	$ 163,359		$ 8		$ 0		$ 288,696		$ 6	$ (125,351)
Ending balance (in shares) at Sep. 30, 2021			84,944,145		0	10,762,566

Condensed Consolidated Statements of Cash Flows (Unaudited) (Q3) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (22,916)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Adjustments to reconcile net income (loss) to cash used in operating activities:
Stock-based compensation	5,400	58,531	1,381	1,818	906
Depreciation and amortization		383	43	47	412
(Gain) loss from unconsolidated subsidiary		354	345	(1,399)	709
Gain from disposal of equity investment	(210)	(20,829)	0
(Gain) loss on extinguishment of debt	0	(790)	75	116	0
Warranty provision		2,118	5,195	7,866	2,057
Warranty asset		(484)	(726)
Bad debt expense		83	0	24	444
Deferred income taxes		0	(2)	(3)	(3)
Other non-cash items		0	43	50	89
Changes in operating assets and liabilities:
Accounts receivable, net		(30,017)	(12,219)	(9,710)	(13,838)
Inventories		(9,590)	(1,523)	2,819	(4,505)
Prepaid and other current assets		(16,609)	(4,351)	(2,847)	(3,154)
Other assets		180	(365)	(1,672)	(156)
Accounts payable		(535)	4,009	8,936	7,781
Accruals and other current liabilities		21,243	13,825	7,162	3,389
Accrued interest - related party debt		(207)	(112)	(78)	(289)
Deferred revenue		(13,374)	(14,108)	3,107	19,683
Other non-current liabilities		904	386	496	1
Other, net		(1,068)	(338)	(298)	(1)
Net cash used in operating activities		(92,414)	(14,638)	(511)	(254)
Cash flows from investing activities:
Purchases of property and equipment		(778)	0	(256)	(18)
Proceeds from disposal of equity method investment		22,332	0
Proceeds from Divestiture of Interest in Subsidiaries and Affiliates				2,124	0
Net cash provided by (used in) investing activities:		21,554	0	1,868	(18)
Cash flows from financing activities:
Proceeds from borrowings		0	784	784	1,000
Repayments of borrowings		(1,000)	(4,000)	(7,000)	0
Repurchase and retirement of common stock		(54,155)	0
Offering cost paid		(5,942)	0
Deferred financing costs for revolving credit facility		(2,077)	0
Proceeds from stock issuance		241,314	30,000	30,000	6,000
Net cash provided by (used in) financing activities		178,140	26,784	23,784	7,000
Effect of exchange rate changes on cash and restricted cash		9	(20)	(3)	0
Net increase in cash and restricted cash		107,289	12,126	25,138	6,728
Cash and restricted cash at beginning of period		33,373	8,235	8,235	1,507
Cash and restricted cash at end of period	140,662	140,662	20,361	33,373	8,235
Supplemental disclosures of cash flow information:
Purchase of property and equipment included in account payable		40	0
Non-cash gain on extinguishment of debt from PPP loan forgiveness		(790)	0
Gain (loss) on extinguishment of debt	0	790	(75)	(116)	0
Cash paid during the period for interest		332	350	350	708
Reconciliation of cash and restricted cash at period end
Cash	140,662	140,662	32,359	32,359	7,221
Restricted cash	0	0	1,014	1,014	1,014
Total cash and restricted cash	$ 140,662	$ 140,662	$ 33,373	$ 33,373	$ 8,235

Description of Business (FY)	9 Months Ended	12 Months Ended
Description of Business (FY)	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. Description of Business FTC Solar, Inc. (the “Company”, “we”, “our”, or “us”) was founded in 2017 and is incorporated in the state of Delaware. We are a global provider of advanced solar tracker systems, supported by proprietary software and value-added engineering services. Our mission is to provide differentiated products, software and services that maximize energy generation and cost savings for our customers, and to help facilitate the continued growth and adoption of solar power globally. Trackers significantly increase the amount of solar energy produced at a solar installation by moving solar panels throughout the day to maintain an optimal orientation relative to the sun. Our tracker systems are currently marketed under the Voyager brand name (“Voyager Tracker” or “Voyager”). Voyager is a next-generation two-panel in-portrait single-axis tracker solution that we believe offers industry-leading performance and ease of installation. We are a team of dedicated renewable energy professionals focused on delivering cost reductions to our clients across the solar project development and construction cycle. With significant US and worldwide project installation experience, our differentiated offerings drive value for solar solutions spanning a range of applications including ground mount, tracker, canopy, and rooftop. The Company is headquartered in Austin, Texas and has subsidiaries in Australia, India, Singapore, and South Africa. Initial Public Offering and Related Transaction The Company’s common stock began trading on the Nasdaq Stock Exchange on April 28, 2021, under the symbol “FTCI” and on April 30, 2021, the Company completed its Initial Public Offering (“IPO”). In connection with the IPO, the Company issued and sold 19,840,000 shares of its common stock at a public offering price of $13.00 per share. Prior to the completion of the IPO, the Board of Directors and Stockholders approved an approximately 8.25-for-1 forward stock split (the “Forward Stock Split”) of the Company’s shares of common stock which became effective on April 28, 2021. The Company received aggregate proceeds of $241.2 million from the IPO, net of the underwriting discount and commissions and before offering costs and used $54.2 million to purchase and retire an aggregate of 4,455,384 shares of our common stock, some of which resulted from the settlement of certain vested Restricted Stock Units (“RSUs”) and the exercise of certain options in connection with the IPO at the IPO price less underwriting discounts and commissions Offering costs, including legal, accounting, printing and other IPO-related costs, were reclassified to Additional paid-in capital and recorded against the proceeds from the offering during the quarter ended June 30, 2021. JOBS Act Accounting Election We are an emerging growth company, as defined in the Jumpstart Our Business Startups (JOBS) Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards until such time as those standards apply to private companies. Accordingly, we have elected to use the extended transition period to adopt new or revised accounting standards.	1. Description of Business FTC Solar, Inc. (the “Company”, “we”, “our”, or “us”) was founded in 2017 and is incorporated in the state of Delaware. The Company is a team of dedicated renewable energy professionals focused on delivering cost reductions to our clients across the solar project development and construction cycle. With significant US and worldwide project installation experience, our differentiated offerings drive value for solar solutions spanning a range of applications including ground mount, tracker, canopy, and rooftop. The Company is headquartered in Austin, Texas and has subsidiaries in Australia, India, and Singapore. On January 13, 2017, the Company entered into an asset purchase agreement with SunEdison Utility Holdings, Inc. (“Seller”) to purchase all assets of the Seller, in addition to assuming any liabilities, for a total transaction price of $6 million. SunEdison discontinued its operations and filed for bankruptcy prior to the acquisition date. The assets purchased as part of this acquisition were spun off from SunEdison. As a result of the acquisition, the Company acquired intangible assets in the form of developed technology (AP90 Tracker) and software, and inventory. In connection with the acquisition, the Company was formed in 2017 by the management team behind the AP90 tracker, a first-generation tracker based on a one-panel in-portrait, linked-row design. The management team utilized their design and construction experience, and their experience with installing and operating other competitive tracking solutions, to create the next-generation Voyager Tracker, which achieved product certification in 2019.

Summary of Significant Accounting Policies (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

These unaudited condensed consolidated financial statements include the results of the Company and its wholly owned subsidiaries and have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). Intercompany accounts and transactions have been eliminated upon consolidation.

Forward Stock Split

Use of Estimates

The preparation of the Company’s financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the

disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis.

COVID-19 Pandemic

In March 2020, the World Health Organization declared the novel coronavirus 2019 (“COVID-19”) a global pandemic. The COVID-19 pandemic has had and may continue to have an unfavorable impact on certain parts of our business. The broader implications of the COVID-19 pandemic on our business, financial condition and

results of operations remain uncertain and will depend on certain developments, including the duration and severity of the COVID-19 pandemic, the impact of virus variants, the rate of vaccinations, the COVID-19 pandemic’s impact on our customers and suppliers and the range of governmental and community reactions to the pandemic. We have experienced delays in production and shipments in the current quarter due to an outbreak of COVID at a supplier site and a quarantine imposed on one of our shipping vessels. Due to the nature of the pandemic, we may continue to experience reduced customer demand in certain parts of our business or constrained supply that could materially and adversely impact our business, financial condition, results of operations, liquidity and cash flows in future periods.

Unaudited Interim Financial Information

The accompanying unaudited condensed consolidated financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2020 and 2021, have been prepared in accordance with GAAP for interim financial statements and pursuant to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, all adjustments have been made that are considered necessary for a fair statement of our financial position as of December 31, 2020 and September 30, 2021, our results of operations for the three and nine months ended September 30, 2020 and 2021 and our cash flows for the nine months ended September 30, 2020 and 2021. The condensed consolidated balance sheets as of December 31, 2020 have been derived from the Company’s audited consolidated financial statements. Operating results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021.

Certain information and disclosures normally included in the notes to annual financial statements prepared in accordance with GAAP have been omitted from these interim financial statements pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s final prospectus (the “IPO Prospectus”) dated as of April 29, 2021, and filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Securities Act”).

Concentration of Credit Risk

Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company is exposed to credit risk in the event of default by the financial institutions holding our cash and cash equivalents that are recorded on our balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits its exposure. The Company has not experienced any losses since inception.

The carrying amounts of cash and cash equivalents, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items.

Equity Method Investments

The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Condensed Consolidated Statements of Comprehensive Loss. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions.

The Company evaluates equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. Factors considered by the Company when reviewing an equity method investment for impairment include the length of time and the extent to which the fair value of the equity method investment has been less than cost, the investee’s financial condition and near-term prospects and the intent and ability to hold the investment for a period of time sufficient to allow for anticipated recovery. An impairment that is other-than temporary is recognized in the period identified.

The Company accounts for distributions received from equity method investees under the “nature of the distribution” approach. Under this approach, distributions received from equity method investees are classified on the basis of the nature of the activity or activities of the investee that generated the distribution as either a return on investment (classified as cash inflows from operating activities) or a return of investment (classified as cash inflows from investing activities).

The Company has made an accounting policy election, as a result of disposing of its equity method investment on June 24, 2021, to account for the contingent gains from the earnout provision and projects escrow release only when those amounts become realizable in the periods subsequent to the disposal date. (See Note 7).

Stock -Based Compensation

The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards, stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.

Revenue Recognition

The Company derives its revenue primarily from sale of: (1) Voyager Tracker and customized components of Voyager Tracker, (2) individual parts of Voyager Tracker for certain specific transactions, (3) shipping and handling services, (4) term-based software licenses, (5) maintenance and support services for the term-based software licenses, and (6) subscription services. Product revenue includes revenue from Voyager Tracker and customized components of Voyager Tracker, individual part sales for certain specific transactions, and sale of term-based software licenses. Service revenue includes revenue from shipping and handling services, subscription-based enterprise licensing model, and maintenance and support services in connection with the term-based software licenses.

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

The Company contracts with customers for sale of Voyager Trackers under two different types of arrangements: (1) Purchase Agreements and Equipment Supply Contracts (“Purchase Agreements”) and (2) sale of individual parts of the Voyager Tracker.

The Company’s Purchase Agreements typically include two performance obligations- (1) Voyager Tracker or customized components of Voyager Tracker and (2) shipping and handling services. The deliverables included as part of the Voyager Tracker are predominantly accounted for as one performance obligation, as these deliverables are part of a combined promise to deliver a project. Voyager Tracker and customized components of Voyager Tracker performance obligations in the contract are satisfied over-time as work progresses for its custom assembled Voyager Tracker, utilizing an input measure of progress determined by cost-to-cost measures on these projects as this faithfully depicts the Company’s performance in transferring control.

The revenue for shipping and handling services is recognized over-time based on shipping terms of the arrangements, as this faithfully depicts the Company’s performance in transferring control.

The Company’s sale of individual parts of Voyager Tracker for certain specific transactions include multiple performance obligations consisting of individual parts of the Voyager Tracker. Revenue recognized for the Company’s part sales are recorded at a point in time and recognized when obligations under the terms of the contract with our customer are satisfied. Generally, this occurs with the transfer of control of the asset, which is in line with shipping terms.

Term-based software license revenue

Term-based software license revenue included under product revenue is primarily derived from sale of term-based software licenses that are deployed on the customers’ own servers and have significant standalone functionality. The revenue is recognized upon transfer of control to the customer. The control for term-based software licenses is transferred at the later of delivery to the customer or the software license start date. Term-based software license revenue is immaterial for the three and nine month periods ended September 30, 2020 and September 30, 2021.

Subscription and Maintenance and support services revenue

Subscription revenue is derived from a subscription-based enterprise licensing model with contract terms typically ranging from one to two years and consists of subscription fees from the licensing of Subscription services. Subscription services revenue is immaterial for the three and nine month periods ended September 30, 2020 and September 30, 2021. The hosted on-demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Services revenue includes maintenance and support activities related to term-based software licenses. Support revenue is derived from ongoing security updates, upgrades, bug fixes, and maintenance. A time-elapsed method is used to measure progress because the Company transfers control evenly over the contractual period. Accordingly, the fixed consideration related to these revenues is generally recognized on a straight-line basis over the contract term beginning on the date access is provided.

Cost of Revenue

Cost of revenue consists primarily of costs related to raw materials, freight and delivery, product warranty, and personnel costs (salaries, bonuses, benefits, and stock-based compensation). Personnel costs in cost of revenue include both direct labor costs as well as costs attributable to any individuals whose activities relate to the procurement, installment and delivery of the finished product and services. Deferred cost of revenue results from the timing differences between the costs incurred in advance of the satisfaction of all revenue recognition criteria consistent with our revenue recognition policy.

Warranty

We provide standard assurance type warranties with our Voyager Trackers for periods generally ranging from five to ten years. We record a provision for estimated warranty expenses, net of amounts recoverable from manufacturers, to cost of sales when we recognize revenue. These estimates are based on our historical experience and forward-looking factors including the expected nature and frequency of product failure rates and costs to address future claims. These estimates are inherently uncertain given our relatively short history of sales and changes to our historical or projected warranty experience may result in material changes to our warranty reserve in the future. We do not maintain general or unspecified reserves; all warranty reserves are related to specific projects. All actual or estimated costs incurred in subsequent periods are charged to those established reserves.

Remaining Performance Obligations

Remaining performance obligations relate to contracts that have original expected durations of one year or less. Therefore, the transaction price allocated to performance obligations that are unsatisfied or partially satisfied as of the end of the reporting period are not required to be disclosed under ASC 606.

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of the guidance to help simplify and promote consistent application of GAAP. The Company adopted ASU 2019-12 in the first quarter of 2021, and the adoption had no material impact to the Company’s consolidated financial statements.

New Accounting Pronouncements Not Yet Adopted

currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The Company is currently evaluating the impact that the adoption of ASU 2016-13 will have on its condensed consolidated financial statements and the Company plans to adopt effective January 1, 2023.

In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting. This standard provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. Entities may apply this ASU upon issuance through December 31, 2022 on a prospective basis. The Company is currently evaluating the impact this adoption will have on the Company’s condensed consolidated financial statements and will apply this guidance to transactions and modifications of these arrangements as appropriate.

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

These Consolidated Financial Statements include the results of the Company and its wholly owned subsidiaries and have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). Intercompany accounts and transactions have been eliminated upon consolidation.

Forward Stock Split

On April 28, 2021, we effected an approximately 8.25-for-1 forward split of our issued and outstanding shares of common stock, par value $0.0001 per share. As a result of the Forward Stock Split, one (1) share of common stock issued and outstanding was automatically increased to approximately 8.25 shares of issued and outstanding common stock, without any change in the par value per share. All information related to common stock, stock options, restricted stock awards and earnings per share have been retroactively adjusted to give effect to the Forward Stock Split for all periods presented. This adjustment impacts footnotes 11, 12, 13, and 17. Also on April 28, 2021, the Company amended and restated its certificate of incorporation which increased the number of authorized shares of all classes of stock to 860,000,000, consisting of (i) 850,000,000 shares of Common Stock, par value $0.0001 per share and (ii) 10,000,000 shares of Preferred Stock, par value $0.0001 per share.

Reclassification

Certain amounts in the prior periods presented have been reclassified to conform to the current period financial statement presentation. These reclassifications have no effect on previously reported results of operations.

Liquidity

Our management believes that our existing capital, which includes our cash and restricted cash is sufficient for us to remain in operation for at least one year from the date of issuance of these consolidated financial statements. While management believes that the Company’s existing sources of liquidity are adequate to fund operations through twelve months from the date the financials are available to be issued, the Company may need to raise additional debt or equity financing to fund operations.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. Estimates are used for calculating the measure of progress of Voyager tracker projects and deriving the standalone selling prices of the individual performance obligations when determining the revenue recognition, allowances for doubtful accounts, useful lives of intangible assets, fair value of investments, warranty liabilities, income taxes and stock-based compensation. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that it believes are reasonable under the circumstances, including assumptions as to future events. Actual results could differ from those estimates.

COVID-19 Impact

The COVID-19 pandemic has caused, and continues to cause, widespread economic disruption and has impacted the Company in a number of ways, most notably governmental authorities in the United States and around the world have imposed various restrictions designed to slow the pace of the pandemic, including restrictions on travel and other restrictions that prohibit employees from going to work. The Company expects the extent of the impact on its financial and operational results will depend on the duration and severity of the economic disruption caused by the COVID-19 pandemic.

The Company considered the impacts of the COVID-19 pandemic on its significant estimates and judgments used in applying its accounting policies. In light of the pandemic, there is a greater degree of uncertainty in applying these judgments and depending on the duration and severity of the pandemic, changes to its estimates and judgments could result in a meaningful impact to its consolidated financial statements in future periods.

Functional Currency

The reporting currency of the Company is the U.S. dollar. The Company determines the functional currency of each subsidiary in accordance with ASC 830, Foreign Currency Matters, based on the currency of the primary economic environment in which each subsidiary operates. The Company translates the assets and liabilities of its non-U.S. dollar functional currency subsidiary into U.S. dollars using exchange rates in effect at the end of each period. Revenues and expenses for these subsidiaries are translated using rates that approximate those in effect during the period. Gains and losses from these translations are recognized in cumulative translation adjustment included in “Accumulated other comprehensive loss” in Stockholders’ equity (deficit) on the Consolidated Balance Sheets.

The Company remeasures monetary assets and liabilities that are not denominated in the functional currency at exchange rates in effect at the end of each period. Transaction gains and losses were not material for the years ended December 31, 2019 and 2020.

Cash

As of December 31, 2019 and 2020, the Company had $7.2 million and $32.4 million in cash, respectively.

As of December 31, 2019 and 2020, the Company had $1.0 million in restricted cash. The restricted cash represents cash collateral posted with providers of letters of credit.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and accounts receivable. The Company maintains its cash accounts with financial institutions where, at times, deposits exceed federal insurance limits. The Company extends credit to customers in the normal course of business. The Company performs credit analyses and monitors the financial health of its customers to reduce credit risk.

The Company’s accounts receivables are derived from revenue earned from customers primarily located in the United States of America and Asia Pacific.

During the year ended December 31, 2019, three customers accounted for 59%, 21% and 13% of total revenue, respectively. During the year ended December 31, 2020, four customers accounted for 21%, 19%, 10% and 10% of total revenue, respectively. No other customers accounted for more than 10% of total revenues for these periods.

As of December 31, 2019, three customers accounted for 49%, 23% and 18% of accounts receivable, respectively. As of December 31, 2020, three customers accounted for 32%, 25% and 14% of accounts receivable, respectively. No other customers accounted for more than 10% of accounts receivable for these periods.

Equity Method Investments

The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Consolidated Statement of Operations. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions.

Fair Value of Financial Instruments

The Company’s financial instruments consist of its cash, restricted cash, investments, accounts receivable, accounts payable, and accrued liabilities. Cash, accounts receivable, accounts payable, and accrued liabilities are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment date.

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., the “exit price”) in an orderly transaction between market participants at the measurement date. A hierarchy for inputs used in measuring fair value has been defined to minimize the use of unobservable inputs by requiring the use of observable market data when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on active market data. Unobservable inputs are inputs that reflect the Company’s assumptions about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances.

The fair value hierarchy prioritizes the inputs into three broad levels:

•	Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities.

•

Level 2: Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability.

•	Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company accounts for long-term debt on an amortized cost basis. The carrying value of the long-term debt held by the Company approximates fair value because the interest rate is reflective of currently applicable market rates for a debt with similar terms and amount.

The Company did not hold any financial instruments measured at fair value on a recurring basis categorized within the fair value hierarchy at December 31, 2019 and 2020.

Inventories

Inventories are stated at lower of cost or net realizable value, with costs computed on a first-in, first-out basis. The Company periodically reviews its inventories for excess and obsolete items and adjusts carrying costs to estimated net realizable values when they are determined to be less than cost. Inventories held at December 31, 2019 and 2020 consist of raw material aggregating to $0.2 million and $0.0 million, respectively, and finished goods aggregating to $4.3 million and $1.7 million, respectively.

Leases

Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), as amended (“ASC 842”). The Company determines if a contract is a lease or contains a lease at the inception of the contract and reassesses that conclusion if the contract is modified. All leases are assessed for classification as an operating lease or a finance lease. Operating lease right-of-use (“ROU”) assets are included within other assets on the Company’s Consolidated Balance Sheet. Operating lease liabilities are separated into a current portion and included within accrued expenses and other liabilities on the Company’s Consolidated Balance Sheet, and a non-current portion included within other non-current liabilities on the Company’s Consolidated Balance Sheet. The Company does not have any finance lease ROU assets or liabilities.

ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. The Company does not obtain and control its right to use the identified asset until the lease commencement date.

The Company’s lease liabilities are recognized at the applicable lease commencement date based on the present value of the lease payments required to be paid over the lease term. Because the rate implicit in the lease is not readily determinable, the Company generally uses its incremental borrowing rate to discount the lease payments to present value. The estimated incremental borrowing rate is derived from information available at the lease commencement date. The Company factors in publicly available data for instruments with similar characteristics when calculating its incremental borrowing rates. The Company’s ROU assets are also recognized at the applicable lease commencement date. The ROU asset equals the carrying amount of the related lease liability, adjusted for any lease payments made prior to lease commencement and lease incentives provided by the lessor. Variable lease payments are expensed as incurred and do not factor into the measurement of the applicable ROU asset or lease liability.

The term of the Company’s leases equals the non-cancellable period of the lease, including any rent-free periods provided by the lessor, and also include options to renew or extend the lease (including by not terminating the lease) that the Company is reasonably certain to exercise. The Company establishes the term of each lease at lease commencement and reassesses that term in subsequent periods when one of the triggering events outlined in ASC 842 Leases occurs. Operating lease cost for lease payments is recognized on a straight-line basis over the lease term.

The Company’s lease contracts often include lease and non-lease components. For facility leases, the Company has elected the practical expedient offered by the standard to not separate lease from non-lease components and accounts for them as a single lease component. For the Company’s other contracts that include leases, the Company accounts for the lease and non-lease components separately.

The Company has elected, for all classes of underlying assets, not to recognize ROU assets and lease liabilities for leases with a term of twelve months or less. Lease cost for short-term leases is recognized on a straight-line basis over the lease term.

Property and Equipment

Property and equipment, net is stated at cost less accumulated depreciation. Property and equipment is included in other assets on the Consolidated Balance Sheets. Depreciation of property and equipment is computed using the straight-line method over the estimated useful lives of the assets, which range from two to five years. When assets are retired or otherwise disposed of, the cost and accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is recorded in the consolidated statement of operations and comprehensive loss in the period realized. Maintenance and repair costs, that do not extend the life or improve an asset, are expensed as incurred. Depreciation and amortization expenses for property and equipment was immaterial for the years ended December 31, 2019 and 2020.

Capitalized Software

Capitalized software, stated at cost less accumulated amortization, includes capitalizable application development costs associated with internally developed software. Capitalized software is included in other assets on the Consolidated Balance Sheets. Amortization of capitalized software is computed using the straight-line method over the estimated useful life of the software, generally three years, and recognized beginning the general availability date. There was no amortization expense for the years ended December 31, 2019 and 2020.

Long Lived Assets

The Company evaluates its long-lived assets, which consist of property and equipment, right-of-use assets, and acquired intangible assets, for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Intangible assets consist of software tools, licenses, and intellectual property, which are amortized over the period of estimated useful lives using the straight-line method. No significant residual value is estimated for intangible assets. Recoverability of these assets is measured by comparison of the carrying amount of such assets (or asset group) to the future undiscounted cash flows the asset (or asset group) are expected to generate. If the total of the future undiscounted cash flows is less than the carrying amount of an asset (or asset group), the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired assets. The Company also evaluates the estimated remaining useful lives of intangible assets to assess whether a revision to the remaining periods of amortization is required. No assets were determined to be impaired during the years ended December 31, 2019 and 2020.

Revenue Recognition

Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, (Topic 606), as amended (“ASC 606”) using full retrospective approach. The Company recognizes revenue from the sale of Voyager Single-Axis Solar Tracker (the “Voyager Tracker”), software, and engineering services. Revenue from engineering services is immaterial for the years ended December 31, 2020 and 2019. The Company recognizes revenue when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services by following a five-step process, (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when or as the Company satisfies a performance obligation, as further described below.

Identify the contract with a customer: A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the products and services to be transferred and identifies the payment terms related to these products and services, (ii) the contract has commercial substance and, (iii) the Company determines that collection of substantially all consideration for products and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. In assessing the recognition of revenue, the Company also evaluates whether two or more contracts should be combined and accounted for as one contract and if the combined or single contract should be accounted for as multiple performance obligations which could change the amount of revenue and profit (loss) recorded in a period. Change orders may include changes in specifications or design, manner of performance, equipment, materials, scope of work, and/or the period of completion of the project. The Company analyzes its change orders to determine if they should be accounted for as a modification to an existing contract or a new stand-alone contract.

The Company’s change orders are generally modifications to existing contracts and are included in the total estimated contract revenue when it is probable that the change order will result in additional value that can be reliably estimated and realized.

Identify the performance obligations in the contract: The Company enters into contracts that can include various combinations of products and services, which are either capable of being distinct and accounted for as separate performance obligations or as one performance obligation, as the majority of tasks and services is part of a single project or capability. However, determining whether products or services are considered distinct performance obligations that should be accounted for separately versus together may sometimes require significant judgment. Performance obligations include the sale of Voyager Tracker, customized components of Voyager Tracker, sale of

individual parts of Voyager Tracker for certain specific transactions, shipping and handling services, sale of term-based software licenses, maintenance, and support services in connection with the term-based software licenses and sale of software as a service subscription (“Subscription services”)

Determine the transaction price: The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring services to the customer. Such amounts are typically stated in the customer contract and to the extent that the Company identifies variable consideration, the Company estimates the variable consideration at the onset of the arrangement as long as it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. None of the Company’s contracts contain a significant financing component. Taxes collected from customers and remitted to governmental authorities are not included in revenue. The majority of the Company’s contracts do not contain variable consideration provisions as a continuation of the original contract.

Allocate the transaction price to performance obligations in the contract: Once the Company has determined the transaction price, the total transaction price is allocated to each performance obligation in a manner depicting the amount of consideration to which the Company expects to be entitled in exchange for transferring the good(s) or service(s) to the customer. The Company allocates the transaction price to each performance obligation identified in the contract on a relative standalone selling price basis.

The Company uses the expected cost-plus margin approach based on hardware, labor, and related overhead cost to estimate the standalone selling price of the Voyager Tracker, customized components of Voyager Tracker, and individual parts of Voyager Tracker for certain specific transactions. The Company uses the adjusted market assessment approach for all other performance obligations except shipping, handling, and logistics. For shipping, handling, and logistics performance obligation, the Company uses residual approach to calculate the standalone selling price, because of the nature of highly variable and broad range of prices it charges to various customers for this performance obligation in the contracts.

Recognize revenue when or as the Company satisfies a performance obligation: For each performance obligation identified, we determine at contract inception whether we satisfy the performance obligation over time or at a point in time. The Company’s performance obligations for the customer specific Voyager Tracker and customized components of Voyager Tracker are satisfied over-time as the work progresses because the Company’s performance does not create an asset with an alternative use to the Company, due to the highly customized nature of the product, and the Company has an enforceable right to payment for performance completed to date. The Company’s performance obligation for shipping and handling services is satisfied over-time as the services are delivered over the term of the contract. The Company’s subscription services sales/ other services are recognized on a straight-line basis over the contract period. The Company’s performance obligations for individual part sales for certain specific transactions are recognized point-in-time as and when control transfers based on the Incoterms for the contract. The Company’s performance obligations for term-based software licenses are recognized point-in-time as and when control transfers based on delivery of license.

Revenues from Contract with Customers

The Company derives its revenue primarily from sale of: (1) Voyager Tracker and customized components of Voyager Tracker (2) individual parts of Voyager Tracker for certain specific transactions (3) shipping and handling services (4) term-based software licenses, (5) maintenance and support services for the term-based software licenses and (6) subscription services. Product revenue includes revenue from Voyager Tracker and customized components of Voyager Tracker, individual part sales for certain specific transactions, and sale of term-based software licenses. Service revenue includes revenue from shipping and handling services, subscription-based enterprise licensing model, and maintenance and support services in connection with the term-based software licenses.

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

The Company’s contracts with customers for sale of Voyager Trackers under two different types of arrangements: (1) Purchase Agreements and Equipment Supply Contracts (“Purchase Agreements”) and (2) Sale of individual parts of the Voyager Tracker.

The Company’s Purchase Agreements typically include two performance obligations- 1) Voyager Tracker or customized components of Voyager Tracker, and 2) shipping and handling services. The deliverables included as

part of the Voyager Tracker are predominantly accounted for as one performance obligation, as these deliverables are part of a combined promise to deliver a project. Voyager Tracker and customized components of Voyager Tracker performance obligations in the contract are satisfied over-time as work progresses for its custom assembled Voyager Tracker, utilizing an input measure of progress determined by cost-to-cost measures on these projects as this faithfully depicts the Company’s performance in transferring control.

The revenue for shipping and handling services will be recognized over-time based on shipping terms of the arrangements, as this faithfully depicts the Company’s performance in transferring control.

Term-based software license revenue

Term-based software license revenue included under product revenue is primarily derived from sale of term-based software licenses that are deployed on the customers’ own servers and has significant standalone functionality. The revenue is recognized upon transfer of control to the customer. The control for term-based software license is transferred at the later of delivery to the customer or the software license start date. Term-based software license revenue is immaterial for years ended December 31, 2019 and 2020.

Subscription and Maintenance and support services revenue

Subscription revenue is derived from a subscription-based enterprise licensing model with contract terms typically ranging from one to two years and consists of subscription fees from the licensing of Subscription services. Subscription services revenue is immaterial for years ended December 31, 2019 and 2020. The hosted on-demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Services revenue includes maintenance and support service revenue related to term-based software licenses. Support revenue is derived from ongoing security updates, upgrades, bug fixes, and maintenance. A time-elapsed method is used to measure progress because the Company transfers control evenly over the contractual period. Accordingly, the fixed consideration related to these revenues is generally recognized on a straight-line basis over the contract term beginning on the date access is provided.

Contract liabilities

The timing of revenue recognition, billing, and cash collection results in the recognition of accounts receivable, unbilled receivables, and deferred revenue in the Consolidated Balance Sheet. The Company does not have contract assets as of December 31, 2019 or 2020. The Company may receive advances or deposits from its customers, before revenue is recognized, resulting in contract liabilities. The Company refers to contract liabilities as “deferred revenue” on its consolidated financial statements and related disclosures.

Deferred revenue amounts to $19.9 million and $23.0 million and as of December 31, 2019 and 2020, respectively, consisting of customer deposits related to products and services which were billed in advance. Payment terms vary by the type and location of our customer and the products or services offered. The term between invoicing and when payment is due is not significant. For all Voyager product customers, we require payment before the products or services are delivered to the customer. In most cases, customers prepay for services in advance of our delivery of the related services. During the years ended December 31, 2019 and 2020, the Company recognized $0.2 million and $19.9 million, respectively from deferred revenue recorded at December 31, 2018 and 2019, which represented 100% of the prior year balance for both years.

Cost of Revenue

Cost of revenue consists primarily of costs related to raw materials, freight and delivery, product warranty, and personnel costs (salaries, bonuses, benefits, and stock-based compensation). Personnel costs in cost of revenue includes both direct labor costs as well as costs attributable to any individuals whose activities relate to the procurement, installment and delivery of the finished product and services. Deferred cost of revenue results from the timing differences between the costs incurred in advance of the satisfaction of all revenue recognition criteria consistent with our revenue recognition policy.

Advertising Costs

Advertising costs are expensed as incurred. These amounts are included in selling and marketing expense in the accompanying consolidated statements of operations. Advertising costs were $0.3 million and $0.1 million for the years ended December 31, 2019 and 2020, respectively.

Research and Development Expenses

Research and development costs are expensed as incurred and consist primarily of personnel costs, including salaries, bonuses and benefits, and stock-based compensation related to development of new products and services as well as enhancing system performance, improving product reliability, reducing product cost, and simplifying installation. Research and development costs also include depreciation and allocated overhead.

Warranty

Typically, the sale of Voyager Tracker projects includes parts warranties to customers as part of the overall price of the product. The Company provides standard assurance type warranties for its products for periods generally ranging from five to ten years. The Company records a provision for estimated warranty expenses, net of amounts recoverable from manufacturers, to cost of sales when it recognizes revenue. The Company does not maintain general or unspecified reserves; all warranty reserves are related to specific projects. All actual or estimated materials costs incurred in subsequent periods are charged to those established reserves.

While the Company periodically monitors warranty activities, if actual costs incurred are different from its estimates, the Company may recognize adjustments to provisions in the period in which those differences arise or are identified.

Accounts Receivable and Allowance for Doubtful Debts

Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. The Company generally does not require collateral from its customers; however, in certain circumstances, may require letters of credit, other collateral, additional guarantees or advance payments. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of its customer accounts. The Company regularly reviews its accounts receivable that remain outstanding past their applicable payment terms and establishes allowance and potential write-offs by considering certain factors such as historical experience, industry data, credit quality, age of balances and current economic conditions that may affect a customers’ ability to pay. There was no allowance for doubtful accounts as of December 31, 2019. The allowance for doubtful accounts was not material as of December 31, 2020.

Stock-Based Compensation

The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.

Income Taxes

The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes.

Pursuant to ASC 740, the Company uses the asset and liability method for accounting for income taxes. Under this method, we recognize deferred tax liabilities and assets for the expected future tax consequences of temporary differences between the respective carrying amounts and tax basis of our assets and liabilities.

Deferred tax balances are adjusted to reflect tax rates based on currently enacted tax laws, which will be in effect in the years in which the temporary differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the results of operations in the period of the enactment date.

We establish valuation allowances when necessary to reduce deferred tax assets to the amounts expected to be realized. On a quarterly basis, we evaluate the need for, and the adequacy of, valuation allowances based on the expected realization of our deferred tax assets. The factors used to assess the likelihood of realization include our latest forecast of future taxable income, available tax planning strategies that could be implemented, reversal of taxable temporary differences and carryback potential to realize the net deferred tax assets. See Note 14. Income Taxes, for additional information regarding our income taxes.

We account for uncertain tax positions in accordance with authoritative guidance which prescribes a minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. Our evaluations of tax positions consider various factors including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, information obtained during in process audit activities and changes in facts or circumstances related to a tax position. We accrue interest and penalties related to unrecognized tax benefits as a component of income tax expense.

Deferred Offering Costs

Deferred offering costs, which consist of direct incremental legal, consulting, banking, and accounting fees relating to anticipated equity offerings, are capitalized, and will be offset against proceeds upon the consummation of the offerings. In the event an anticipated offering is terminated, deferred offering costs will be expensed. As of December 31, 2019, the Company had not incurred such costs. As of December 31, 2020, the Company capitalized $1.6 million of deferred offering costs, which are included in other assets in the consolidated balance sheet.

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The Company adopted the new standard effective January 1, 2020. The impact of adoption was not material to the Company’s Consolidated Financial Statements.

New Accounting Pronouncements Not Yet Adopted

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 removes certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of the guidance to help simplify and promote consistent application of GAAP. The guidance is effective for the Company for its fiscal year beginning after December 15, 2021, to the extent the Company remains an emerging growth company, and early adoption is permitted. The Company is currently assessing the impact that the adoption of ASU 2019-12 will have on its consolidated financial statements.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 changes the impairment model for most financial assets and requires the use of an expected loss model in place of the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The update to the standard is effective for the Company for its fiscal year beginning after December 15, 2022, to the extent the Company remains an emerging growth company, and early adoption is permitted. The Company does not expect the adoption of ASU 2016-13 to have a material impact on its consolidated financial statements.

Revenue (FY)	9 Months Ended	12 Months Ended
Revenue (FY)	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	4. Revenue The Company’s product revenue and service revenue is presented in the Condensed Consolidated Statement of Comprehensive Loss. Revenue by geographic region is based on the customer’s location and presented under Note 14. Unbilled revenue and contract liabilities The timing of revenue recognition, billing, and cash collection results in the recognition of accounts receivable, unbilled receivables, and deferred revenue in the Condensed Consolidated Balance Sheets. Unbilled receivables represent an unconditional right to consideration before customers are invoiced. Unbilled receivables are recorded within accounts receivable on the Condensed Consolidated Balance Sheets at the end of the reporting period and consist of $1.2 million and $15.7 million as of December 31, 2020 and September 30, 2021, respectively. The Company’s contracts have a varied range of terms based on the type of products and services sold. Deferred revenue amounts to $23.0 million and $9.6 million as of December 31, 2020 and September 30, 2021, respectively, consisting of customer deposits related to products and services which were billed in advance. The Company expects to recognize 100% of the revenue related to deferred revenue within the next 12 months. During the nine months ended September 30, 2020 and 2021, the Company recognized $19.9 million and $23.0 million, respectively from deferred revenue recorded at December 31, 2019 and 2020.	3. Revenue The Company’s product revenue and service revenue is presented in the consolidated statements of operations. Revenue by geographic region is based on the customer’s location and presented under Note 16. Transaction Price Allocated to the Remaining Performance Obligations The Company’s contracts have a varied range of terms based on the type of products and services sold. As of December 31, 2019 and 2020, the aggregate amount of the transaction price allocated to remaining performance obligations was $19.9 million and $23.0 million, respectively. The Company expects to recognize 100% of the revenue related to remaining performance obligations in the 12 months following year end.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Accrued Expenses and Other Current Liabilities (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accrued Expenses and Other Current Liabilities Abstract

Accrued Expenses and Other Current Liabilities

6. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	December 31, 2020	September 30, 2021
Accrued cost of revenue	$ 7,812	$33,279
Accrued expenses	2,856	3,205
Warranty reserves	3,985	1,183
Accrued compensation	2,869	1,766
Accrued interest expense	28	128
Other	945	685
Total	$18,495	$40,246

4. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2019	2020
Accrued cost of revenue	$2,106	$ 7,812
Accrued expenses	1,644	2,856
Warranty reserves	1,368	3,985
Accrued compensation	177	2,869
Accrued interest expense	47	28
Other	33	945
Total	$5,375	$18,495

Prepaid Expenses and Other Current Assets (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Prepaid Expense and Other Assets, Current [Abstract]

Prepaid Expenses and Other Current Assets

5. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31, 2020	September 30, 2021
Vendor deposits	$4,205	$18,125
Prepaid expenses	1,043	4,060
Deferred cost of revenue	992	—
Surety collateral	113	246
Other current assets	571	1,127
	$6,924	$23,558

5. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	As of December 31,
	2019	2020
Vendor deposits	$1,738	$4,205
Prepaid expenses	209	1,043
Deferred cost of revenue	19	992
Surety collateral^*	1,835	113
Other current assets	47	571
	$3,848	$6,924

*	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Equity Method Investments (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments

7. Sale of Equity Method Investments

On June 24, 2021, the Company disposed of its 4,791,566 Class A common unit interest in Dimension Energy LLC, (“Dimension”) representing approximately 23% of the total outstanding common shares, for approximately $22.0 million, net of a success-based fee of $1.9 million. The Company recognized a gain of $20.8 million due to its disposal of approximately 23% non-controlling interest in Dimension during the nine months ended September 30, 2021. The Company has recognized a net loss from the unconsolidated subsidiary of $0.4 million that is included in the nine months ended September 30, 2021 and recognized net loss of $0.2 million and $0.3 million for the three months and nine months ended September 30, 2020, respectively.

The sales agreement with Dimension includes an earnout provision which provides the potential to receive an additional contingent consideration of up to approximately $14.0 million through December 2024, based on Dimension achieving certain performance milestones. This potential earnout is calculated each quarter starting January 1, 2022. The potential payment is calculated as $200 per the number of kilowatts constituting each Notice To Proceed (NTP) megawatt (MW) achieved during such quarterly earnout period, provided that no earnout amount is payable in respect to the first 100 NTP MW achieved in any earnout year.

The sales agreement also includes a projects escrow release which is an additional contingent consideration to receive $7 million based on Dimension’s completion of certain construction projects currently in progress. The Company has made an accounting policy election to account for the contingent gains from the earnout provision and projects escrow release only when those amounts become realizable in the periods subsequent to the disposal date. On June 29, 2021, the Company made a success-based fee payment in the amount of $1.9 million to two Executive Members of Dimension for entering into voting and support letter agreements and for recommending to all Executive Members of Dimension to support the purchase agreement and the consummation of the transaction on June 24, 2021.

During the three months ended September 30, 2021, the Company received a $0.2 million escrow release payment and recognized the income in accordance with our policy election.

6. Equity Method Investments

Equity method investments are as follows (in thousands, except percentages):

As of December 31, 2019 and 2020, the Company owned 4,791,566 of Class A common interests of Dimension Energy, representing approximately 24% of the total outstanding Class A common shares of Dimension Energy LLC for both years. However, the Company concluded that it is not the primary beneficiary of Dimension as it does not have deemed control of the entity. As a result, it does not consolidate the investee into its consolidated financial statements. The Company accounts for its investment in Dimension Energy using the equity method of

accounting. The difference between fair value and book value of the investee’s assets was entirely attributable to equity method goodwill. For the year ended December 31, 2019, the Company recorded $0.7 million as its share of Dimension’s net loss. For the year ended December 31, 2020, the Company recorded $1.4 million as its share of Dimension’s net income. During fiscal year 2020, the Company received a cash distribution of $2.1 million from Dimension Energy LLC, which was accounted for as a return of investment and reflected as a reduction of the carrying balance of the Company’s equity method investment in the Consolidated Balance Sheet as of December 31, 2020.

Summarized financial information for the Company’s equity method investment is as follows:

Balance sheet (in thousands)

	As of December 31,
	2019	2020
Current assets	$4,466	$10,162
Non-current assets	13,123	9,045
Current liabilities	3,219	12,350
Non-current liabilities	14,344	9,723
Members’ equity (deficit)	25	(2,866)

Statement of operations (in thousands)

	Years Ended December 31
	2019	2020
Revenue	$—	$22,570
Gross profit	—	17,360
Income (loss) from operations	(3,413)	9,185
Net income (loss)	(2,987)	5,933
Share of earnings from equity method investment	(709)	1,399

Intangible Assets, Net (FY)

12 Months Ended

Dec. 31, 2020

Intangible Assets, Net [Abstract]

Intangible Assets, Net

7. Intangible Assets, Net

Acquired intangible assets, comprising of developed technology in the form of software tools, subject to amortization were as follows (in thousands):

		As of December 31,
	Estimated Useful Lives (Years)	2019	2020
Developed technology	3	1,200	1,200
Total intangible assets		1,200	1,200
Less: accumulated amortization		1,167	1,200
Total intangible assets, net		$ 33	$ —

Amortization expense related to intangible assets totaled $0.4 million and $0 million and for the years ended December 31, 2019 and 2020, respectively.

As of December 31, 2020, there is no estimated amortization expense in future periods.

Debt and Other Borrowings (FY)	9 Months Ended	12 Months Ended
Debt and Other Borrowings (FY)	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt and Other Borrowings	8. Debt and Other Borrowings On January 30, 2017, the Company sold $7.0 million in aggregate principal amount of secured five-year promissory notes (“the Notes”) through a private placement. Pursuant to the issuance of the Notes, the Company issued 25,000 shares of common stock for every $250,000 of Notes purchased. The fair value of common stock issued was accounted for as debt discount and was amortized over the term of the Notes. The Notes had a fixed rate of 5% per annum payable at maturity. The Company repaid the principal during the year ended December 31, 2020. On June 17, 2019, the Company entered into a revolving line of credit agreement with the Western Alliance Bank for a total principal amount of $1.0 million and maturity in two years from the date of borrowing. The line of credit had a variable rate of interest, based on movement of prime rate as calculated and published by the Wall Street Journal and required the Company to pay regular monthly payments of all interest accrued as of each payment date. The prime rate at the time of borrowing was at 5.50% per annum. The outstanding balance for the revolving line of credit as of December 31, 2020 was $1 million. The outstanding balance was paid in full and the revolving credit line was closed as of March 31, 2021. On April 30, 2020, the Company received a Paycheck Protection Program (“PPP”) loan pursuant to the Coronavirus Aid, Relief, and Economic Security Act (the “CARES” Act) in the amount of $0.8 million. The PPP loan had a two-year term and bore a fixed interest rate of 1%. Under the terms of the CARES act, the PPP loan was eligible to be forgiven, in part or whole, if the proceeds were used to retain and pay employees and for other qualifying expenditures. On January 20, 2021, the Company received notification from the Small Business Administration that they approved the forgiveness of the full $0.8 million PPP loan. The Company recorded the forgiveness of the PPP loan as a gain on debt extinguishment in other income. On April 30, 2021, the Company entered into a $100 million senior secured revolving credit facility, by and among the Company, as borrower, the several financial institutions from time-to-time parties thereto, and Barclays Bank PLC, as an issuing lender, the swingline lender and as administrative agent (the “Credit Agreement”). The Credit Agreement has an initial three-year term, and it will be used for working capital and for other general corporate purposes. The Company has not made any draws on the revolving credit facility. The Credit Agreement includes the following terms: (i) aggregate commitments of up to $100 million, with letter of credit and swingline sub-limits; (ii) customary base rate of LIBOR plus 3.25% per annum, respectively; (iii) initial commitment fees of 0.50% per annum; (iv) initial letter of credit fees of 3.25% per annum; and (v) other customary terms for a corporate revolving credit facility. The facility is secured by a first priority lien on substantially all of the Company’s assets, subject to certain exclusions, and customary guarantees. The Credit Agreement includes the following financial condition covenants that the Company is required to satisfy: (i) maintain a minimum liquidity of $125 million for each quarter; (ii) maintain a 3.75 times leverage ratio; and (iii) maintain a 1.5 times interest coverage ratio. The leverage and interest coverage ratios will be triggered when the Company achieves $50 million in adjusted EBITDA over a trailing twelve months. Once the leverage and interest coverage ratios are triggered the minimum liquidity will not have a minimum limit. Minimum liquidity includes unrestricted cash plus the undrawn balance of the revolving credit facility. The minimum liquidity covenant was the only financial condition covenant the Company had to satisfy as of the period ended September 30, 2021. As of September 30, 2021, the Company was in full compliance with its financial condition covenant. The Company added $2.1 million in debt issuance costs related to the revolving credit facility which were included in other assets in the Condensed Consolidated Balance Sheets. The debt issuance costs are being amortized over a three-year initial term of the loan. As of September 30, 2021 the unamortized debt issuance costs amounted to $1.8 million. Included in interest expense for the three and nine months periods ended September 30, 2021 are credit facility revolver fees and amortization of debt issuance costs. The Company had $0.1 million in revolver fees and $0.2 million in amortized debt issuance cost for the three months ended September 30, 2021 and $0.2 million in revolver fees and $0.3 million in amortized debt issuance cost for the nine months ended September 30, 2021, respectively. The Company recognized $0.1 million and $0.3 million of interest expense on its debt and other borrowings for the three months ended September 30, 2020 and 2021 and $0.3 million and $0.5 million for the nine months ended September 30, 2020 and 2021, respectively.	8. Debt and Other Borrowings On January 30, 2017, the Company sold $7.0 million in aggregate principal amount of secured five-year promissory notes (“the notes”) through a private placement. Pursuant to the issuance of the promissory notes, the Company issued 25,000 pre-split shares of common stock for every $250,000 of notes purchased. The fair value of common stock issued was accounted for as debt discount and was amortized over the term of the note. The notes bear a fixed rate of 5% per annum payable at maturity. The Company repaid the principal during the year ended December 31, 2020 and recorded a loss on debt extinguishment of $0.1 million in interest expense, net in the Consolidated Statement of Operations. On June 17, 2019, the Company entered into a revolving line of credit agreement with the Western Alliance Bank for a total principal amount of $1.0 million and maturity in two years from the date of borrowing. The line of credit bears a variable rate of interest, based on movement of prime rate as calculated and published by the Wall Street Journal. The Company will pay the regular monthly payments of all interest accrued as of each payment date. The prime rate at the time of borrowing was at 5.50% per annum. As of December 31, 2019 and 2020, the outstanding balance for the revolving line of credit was $1.0 million, payable on June 10, 2021. On April 30, 2020, the Company received a Paycheck Protection Program (“PPP”) loan pursuant to the Coronavirus Aid, Relief, and Economic Security Act (the “CARES” Act) in the amount of $0.8 million. The loan had a two-year term and bore a fixed interest rate of 1%. Under the terms of the CARES act the loan was eligible to be forgiven, in part or whole, if the proceeds were used to retain and pay employees and for other qualifying expenditures. On January 20, 2021, the Company received notification from the Small Business Administration that they approved the forgiveness of the full $0.8 million PPP loan. The Company recognized $0.5 million and $0.5 million interest expense on its debt and other borrowings for the years ended December 31, 2019 and 2020, respectively. The notes and revolving line of credit contain affirmative customary covenants, including maintenance of insurance, notices of claims and litigations, subordination of other lender’s credit and compliance with environmental laws. As of December 31, 2019 and 2020, the Company was in compliance with all required covenants.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1E
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Commitments and Contingencies (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Litigation

The Company may be involved in various claims, lawsuits, investigations, and other proceedings, arising from the normal course of its business. The Company accrues a liability when management believes information available prior to the issuance of financial statements indicates it is probable a loss has been incurred as of the date of the financial statements and the amount of loss can be reasonably estimated. The Company adjusts its accruals to reflect the impact of negotiation, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. Legal costs are expensed as incurred.

On April 21, 2021, FCX Solar, LLC (“FCX”), filed a lawsuit against us in the United States District Court for the Southern District of New York. The complaint alleges breach of contract and tort claims related to a patent license agreement and consulting relationship between FCX and us. FCX seeks damages of approximately $134 million in the lawsuit. On July 2, 2021, we filed a motion to dismiss the tort claims. On July 16, 2021, rather than responding to that motion, FCX filed an amended complaint asserting the same claims as the original

complaint. On July 22, 2021, we advised the court that FTC would stand on its motion to dismiss, and at the request of the court, we filed a revised motion citing the amended complaint. FCX filed its response on August 19, 2021, and we filed a reply and a request for oral argument on September 7, 2021. Discovery in the Southern District of New York matter is ongoing. On May 29, 2021, FCX filed a separate lawsuit against us in the United States District Court for the Western District of Texas, alleging a claim for patent infringement related to U.S. Patent No. 10,903,782. FCX seeks an unspecified amount of damages, including past and future royalties, and injunctive relief. Our answer to that complaint was filed on June 22, 2021, along with our motion to transfer the patent suit to the Southern District of New York to be consolidated with the New York litigation. FCX filed an amended complaint asserting claims for direct patent infringement, indirect infringement by active inducement, and contributory infringement on July 27, 2021, and we filed our answer to that complaint on August 10, 2021. On October 25, 2021, our motion to transfer the case to the Southern District of New York was granted. The Company believes the claims asserted in both lawsuits are without merit, and we plan to vigorously defend against them. The Company and its management considered (a) the facts described above, (b) the preliminary stages of the proceedings and (c) the advice of outside legal counsel on the claims and determined that it is not probable that FCX will prevail on the merits. At this time the Company believes that the likelihood of any material loss related to these matters is remote given the strength of the Company’s defenses

The Company has not recorded any material loss contingency in the Condensed Consolidated Balance Sheets as of December 31, 2020 and September 30, 2021.

Warranties

The Company provides standard warranties on its hardware products. The liability amount is based on actual historical warranty spending activity by type of product, customer, and geographic region, modified for any known differences such as the impact of reliability improvements. As of September 30, 2021, warranty reserves totaling $1.2 million were recorded in accrued expenses and other current liabilities and $4.2 million were recorded in other non-current liabilities, in the Company’s Condensed Consolidated Balance Sheets.

Changes in the Company’s product warranty reserves were as follows (in thousands):

			September 30, 2021
Balance at beginning of period, December 31, 2020			$ 6,811
Warranties issued during the period			2,902
Settlements made during the period			(3,507)
Changes in liability for pre-existing warranties			(783)
Balance at end of period			$ 5,423

9. Commitments and Contingencies

Litigation

The Company may be involved in various claims, lawsuits, investigations, and other proceedings, arising from normal course of its business. The Company accrues a liability when management believes information available prior to the issuance of financial statements indicates it is probable a loss has been incurred as of the date of the financial statement and the amount of loss can be reasonably estimated. The Company adjust its accruals to reflect the impact of negotiation, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. Legal costs are expensed as incurred. Although claims are inherently unpredictable, the Company currently is not aware of any matters that may have a material adverse effect on the business, financial position, results of operations, or cash flows. The Company has not recorded any material loss contingency in the Consolidated Balance Sheets as of December 31, 2019 and 2020.

Warranties

The Company provides standard warranties on its hardware products. The liability amount is based on actual historical warranty spending activity by type of product, customer, and geographic region, modified for any known differences such as the impact of reliability improvements. As of December 31, 2019 and 2020, warranty reserves totaling $1.4 million and $4.0 million were recorded in accrued expenses and other current liabilities, respectively and $0.7 million and $2.8 million and were recorded in other non-current liabilities, respectively, in the Company’s Consolidated Balance Sheets.

Changes in the Company’s product warranty reserves were as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance at beginning of period	$ —	$ 2,057
Warranties issued during the period	2,057	7,866
Settlements made during the period	—	(3,111)
Changes in liability for pre-existing warranties	—	(1)
Balance at end of period	$2,057	$ 6,811

Leases (FY)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Leases

10. Leases

The Company leases office space under operating leases with lease terms ranging from twelve to thirty-nine months. Additionally, the Company entered into a ground lease agreement for specific testing facility on the Solar Technology Acceleration Center. The Company does not have any finance leases.

Operating lease expense for the years ended December 31, 2019 and 2020 was $0.1 million and $0.2 million, respectively. Lease expense related to leases with terms of one year or less that are not recognized on the Company’s Consolidated Balance Sheet was immaterial for both years.

Supplemental balance sheet information related to leases was as follows (in thousands):

	As of December 31,
Reported as:	2019	2020
Assets:
Operating lease right of use assets (included in Other assets)	$43	$571
Liabilities:
Operating lease liabilities, current portion (included in Accrued expenses and other current liabilities)	$11	$242
Operating lease liabilities, non-current (included in Other non-current liabilities)	27	355
Total operating lease liabilities	$38	$597

Supplemental information related to operating leases was as follows (in thousands):

	As of December 31,
	2019	2020
Cash payments for operating leases	$38	$140
New operating lease assets obtained in exchange for operating lease liabilities	$42	$672

As of December 31, 2019 and 2020, the weighted-average remaining lease term for operating leases is 1.88 years and 3.08 years, respectively. As of December 31, 2019 and 2020, the weighted-average discount rate for operating leases was 5%.

Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 are as follows (in thousands):

2021			$266
2022			241
2023			128
Total future lease payments			$635
Less imputed interest			(38)
Total lease liability			$597

Common Stock (FY)	12 Months Ended
Common Stock (FY)	Dec. 31, 2020
Common Stock [Abstract]
Common Stock	11. Common Stock The Certificate of Incorporation, as amended as of December 31, 2017 (the “Certificate of Incorporation”), authorizes the Company to issue 98,960,064 shares of $ 0.0001 par value of Common Stock. Holders of Common Stock are entitled to dividends, as and when, declared by the Board of Directors, subject to the rights of the holders of all classes of stock outstanding having priority rights as to dividends. There have been no dividends declared to date. The holders of the Common Stock are entitled to one vote for each share of Common Stock; provided that, except as otherwise required by law, holders of Common Stock (in such capacity) shall not be entitled to vote on any amendment to the Certificate of Incorporation that relates solely to the terms of one or more outstanding series of Preferred Stock if the holders of such affected series are entitled, either separately or together with the holders of one or more other such series, to vote thereon pursuant to the Certificate of Incorporation. In March 2020, the Company sold 9,162,976 post-split shares of common stock at $3.27 per share for an aggregate purchase price of $30,000,024. The proceeds are available for working capital and other corporate purposes. Related Party Stock Repurchase On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from a founder of the Company. The repurchase of these shares is recorded as treasury stock on the Company’s consolidated balance sheets as of December 31, 2020 and is intended to be added to the overall pool of stock available to be utilized for future option/stock award issuances to other employees of the organization.

Stock Plans (FY)

12 Months Ended

Dec. 31, 2020

Stock Plans [Abstract]

Stock Plans

12. Stock Plans

On January 9, 2017, the Company’s board of directors adopted the 2017 Stock Incentive Plan (the “Plan”). The Plan offers employees, directors and selected service providers to acquire equity in the Company in the aggregate number of shares through awards of Options, Restricted Stock Awards (“RSA”), Stock Appreciation Rights, Restricted Stock Units (“RSU”), and Other Stock Awards, at exercise prices not less than the fair market value at date of grant. As of December 31, 2020, 24,534,509 post-split shares were authorized to be issued under 2017 Stock Incentive Plan. Generally new shares are issued from the Company’s balance of authorized Common Stock from the 2017 Stock Incentive Plan to satisfy stock option exercises and vesting of awards. The Company also holds Treasury Shares available for issuance for awards under its stock-based benefit plans.

In December 2020, the Company entered into an amendment agreement with one of the Founders to modify the vesting of his Restricted Stock Awards. The amended plan resulted in modification of his outstanding equity awards by changing the vesting schedule. No incremental compensation expense was recorded as a result of this modification given that modification was limited to change in vesting schedule and did not impact the probability of vesting.

The following table summarizes stock option activity under the Plan and related information:

	Options Outstanding
	Number of Shares	Weighted Average Exercise Price	Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding - December 31, 2019	8,081,739	$0.22
Granted during the year	525,725	0.48
Exercised or released	—	—
Cancelled or forfeited	82,467	0.07
Expired	—	—
Balances - December 31, 2020	8,524,997	$0.23	7.51	$25,785
Vested and expected to vest - December 31, 2020	8,524,997	$0.23	7.51	$25,785
Exercisable - December 31, 2020	5,379,164	$0.16	7.11	$16,693

Stock options generally vest over four years from the date of grant, and are based only on service vesting conditions, except in the event of a change in control as defined under the Plan which would provide for accelerated exercisability. The options expire no later than ten years of grant date. The weighted-average grant date fair value of options granted to employees during the years ended December 31, 2019 and 2020 was $1.29 and $2.86, respectively. The aggregate intrinsic values of options exercised during the years ended December 31, 2019 and 2020 was zero for both years.

During fiscal 2020, the Company issued performance-based restricted stock units. RSUs have performance and service vesting conditions, which must both be satisfied in order to vest. Service vesting conditions for RSUs provide for vesting over four years from the date of grant except for 9.9 million RSUs that were issued during the year which have a service period up to the date of completion of the liquidity event. RSUs vest upon the completion of a liquidity event, either an initial public offering or sale event. No RSUs vested during the years ended December 31, 2019 and 2020, as the performance conditions are not probable of occurring. Therefore, no stock-based compensation cost has been recognized related to the RSUs granted as of December 31, 2020. Total unrecognized stock-based compensation cost of $40.8 million related to unvested RSUs is expected to be recognized upon vesting.

Under the Stock Plan, an RSA is an award of shares of common stock that may be subject to restrictions on transferability and other restrictions as the Board of Directors determine in its sole discretion on the date of grant. The Company has issued RSAs only to Founders and the restrictions are related to transferability, along with the standard service condition of four years required for vesting. During the years ended December 31,

2019 and 2020, the Company recognized stock-based compensation expense of $0.2 million and $0.2 million, respectively, related to RSAs issued under the Plan. As of December 31, 2019 and 2020, there was $0.2 million and $0.1 million, respectively, of total unamortized compensation cost related to RSAs under the Plan.

The following summarizes restricted stock activity under the Plan:

	Unvested Restricted Stock Units		Unvested Restricted Stock Awards
	Number of Shares	Weighted- Average Intrinsic Value	Number of Shares	Weighted- Average Grant Date Fair Value
Unvested as of December 31, 2019	824,667	$1.64	4,424,652	$0.07
Granted	12,201,611	3.26	—	—
Vested	—	—	3,255,052	0.07
Forfeited or canceled	82,467	3.26	—	—
Unvested as of December 31, 2020	12,943,811	$ 3.16	1,169,600	$0.07

Stock-Based Compensation Expense

The Company recognized stock-based compensation expense under the Plan (in thousands):

	Years Ended December 31,
	2019	2020
Cost of revenue	$176	322
General and administrative	653	1,401
Research and development	51	57
Selling and marketing	26	38
Total stock-based compensation expense	$906	1,818

Total unamortized stock-based compensation expense as of December 31, 2020 was $44.5 million and is expected to be recognized over a weighted average period of approximately 3.04 years. This includes 9.9 million shares granted during the year that as described above have a service period through the date of the liquidity event.

Determination of Fair Value

The Company estimates the fair value of share-based compensation for stock options utilizing the Black-Scholes option-pricing model, which is dependent upon several variables, discussed below. These amounts are estimates and, thus, may not be reflective of actual future results, nor amounts ultimately realized by recipients of these grants. The Company recognizes compensation on a straight-line basis over the requisite vesting period for each award.

Fair Value of Common Stock: The fair value of the shares of common stock underlying the stock-based awards has historically been determined by the board of directors, with input from management. Because there has been no public market for the Company’s common stock, the board of directors has determined the fair value of the common stock on the grant date of the stock-based award by considering a number of objective and subjective factors, including 409A valuations of the Company’s common stock, valuations of comparable companies, sales of the Company’s common stock to unrelated third parties, operating and financial performance, the lack of liquidity of the Company’s capital stock, and general and industry-specific economic outlook. The fair value of the underlying common stock will be determined by the board of directors until such time as the Company’s common stock is listed on an established stock exchange or national market system.

Expected Term: The expected term represents the period that the Company’s stock-based awards are expected to be outstanding and was calculated as the average of the option vesting and contractual terms, based on the simplified method. The simplified method deems the term to be the average of the time-to-vesting and the contractual life of the options.

Expected Volatility: Since the Company does not have a trading history of its common stock, the expected volatility was derived from the average historical stock volatilities of several public companies within the Company’s industry that its considers to be comparable to its business over a period equivalent to the expected term of the stock option grants.

Risk-Free-Interest-Rate: The Company bases the risk-free interest rate on the implied yield available on US Treasury zero-coupon issues with remaining term equivalent to expected term.

Expected Dividend: The Company has not issued any dividends in its history and does not expect to issue dividends over the life of the options and, therefore, has estimated the dividend yield to be zero.

The fair value of stock options granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:

	Years Ended December 31,
	2019	2020
Expected term (years)	5.66–6.09	5.99–6.17
Expected volatility	52.01%—54.10%	51.52%—51.58%
Risk-free interest rate	1.63%—2.3%	1.60%—1.61%
Expected dividends	—	—
Grant date fair value per option	$1.27—$1.30	$2.85—$2.86

Net Loss Per Share (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Net Loss Per Share [Abstract]

Net Loss Per Share

12. Net loss per share

The table below sets forth the computation of basic and diluted loss per share. All shares and per share amounts have been adjusted for an approximately 8.25-for-1 share forward stock split which took effect on April 28, 2021 (in thousands, except per share amounts):

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
Basic and diluted:
Net loss	$ (2,840)	$ (22,916)	$ (6,196)	$ (82,707)
Basic weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Diluted weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Basic loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)
Diluted loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)

For purposes of computing diluted net income per share, weighted-average common shares do not include potentially dilutive securities that are anti-dilutive. The following potentially dilutive securities were excluded (in thousands):

	As of September 30,
	2020	2021
Shares of common stock issuable under stock option plans outstanding	8,566	9,610
Shares of common stock issuable upon vesting of restricted stock awards	13,622	5,598
Potential common shares excluded from diluted net loss per share	22,188	15,208

13. Net loss per share

The table below sets forth the computation of basic and diluted loss per share (in thousands, except per share amounts):

	Years Ended December 31,
	2019	2020
Basic and diluted:
Net loss	$(13,495)	$(15,924)
Weighted-average number of common shares outstanding	62,043	68,811
Basic and diluted loss per share	$(0.22)	$(0.23)

For purposes of computing diluted net loss per share, weighted-average common shares do not include potentially dilutive securities that are anti-dilutive. The following potentially dilutive securities were excluded (in thousands):

	As of December 31,
	2019	2020
Shares of common stock issuable under stock option plans outstanding	8,082	8,525
Shares of common stock issuable upon vesting of restricted stock awards	5,249	14,122
Potential common shares excluded from diluted net loss per share	13,331	22,647

Income Taxes (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

For the three months ended September 30, 2020 and 2021, the Company recorded an income tax expense of $0.02 million and $0.04 million respectively. For the nine months ended September 30, 2020 and 2021, the Company recorded an income tax benefit of $0.12 million and income tax expense of $0.14 million, respectively. Income tax expense recorded for three and nine months ended September 30, 2020 and 2021, was lower than the statutory tax rate of 21% primarily due to a valuation allowance established against the U.S. deferred tax assets.

As of September 30, 2021, the Company had total unrecognized tax benefits of approximately $0.1 million. All of our gross unrecognized tax benefits, if recognized, would affect our effective tax rate. We recognize accrued interest and penalties related to unrecognized tax benefits as a component of income tax expense. As of September 30, 2021, the Company had not accrued any interest or penalties related to unrecognized tax benefits.

14. Income Taxes

The following table summarizes our U.S. and foreign income (loss) before income taxes (in thousands):

	Years Ended December 31,
	2019	2020
U.S.	$(13,534)	$(16,269)
Foreign	—	262
Total loss before income taxes	$(13,534)	$(16,007)

For the years ended December 31, 2019 and 2020, the pre-tax loss attributable to foreign operations was insignificant. The provision for income tax expense (benefit) was composed of the following (in thousands):

	Years Ended December 31,
	2019	2020
Current
Federal	$—	$(159)
State	(37)	1
Foreign	—	78
Deferred
Federal	(2)	(3)
State	—	—
Total income tax expense/(benefit)	$(39)	$(83)

The difference between the income tax expense (benefit) derived by applying the federal statutory income tax rate to our income (loss) before income taxes and the amount recognized in our consolidated financial statements is as follows (in thousands):

	Years Ended December 31,
	2019	2020
Income tax expense (benefit) derived by applying the federal statutory tax rate to income (loss) before income taxes	$(2,842)	$(3,362)
State taxes, net of federal	(551)	(215)
Research and experimentation tax credit	(118)	(179)
Valuation allowance	3,184	3,523
Stock compensation	225	406
Dividends received deduction	—	(308)
Permanent differences and other	63	52
	$(39)	$(83)

Deferred income taxes reflect the net tax effects of loss and credit carryforwards and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company’s deferred income tax assets and liabilities were comprised of the following (in thousands):

	As of December 31,
	2019	2020
Deferred tax assets:
Fixed assets and intangibles	$156	$135
Leases	—	106
Accrued expenses	333	2,066
Net operating loss carryforward	4,626	6,679
Capital loss carryforward	501	—
Investment difference	—	148
R&D credit carryforward	181	325
Subtotal	5,797	9,459
Less valuation allowance	(5,774)	(9,297)
Total deferred tax asset	23	162
Deferred tax (liabilities):
Investment difference	(15)	—
Leases	—	(101)
Prepaid expenses	(11)	(61)
Total deferred tax (liability)	(26)	(162)
Net deferred tax asset (liability)	$(3)	$—

The net change in the total valuation allowance for the years ended December 31, 2019 and 2020, was an increase of $3.1 million and $3.5 million, respectively. In assessing the realizability of deferred tax assets, management considered whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considered the scheduled reversal of deferred tax liabilities, carryback potential, projected future taxable income and tax planning strategies in making this assessment. After consideration of these factors and based upon the level of historical taxable income, management believes it is more likely than not that the Company will not realize the benefits of these deductible differences at December 31, 2020.

The Company has federal net operating loss carryforwards of approximately $27.8 million at December 31, 2020. These loss carryforwards have an indefinite carryforward period. The Company also has state net operating loss carryforwards of approximately $17.0 million, which begin to expire in 2034.

The Company has federal R&D Credit carryforwards of approximately $0.4 million at December 31, 2020, which begin to expire in 2038.

The Company is subject to U.S. federal income tax, as well as income tax in multiple state and foreign jurisdictions. The tax returns for years 2017 and beyond remain open for examination. As of December 31, 2020, the Company is not currently under audit by any taxing authority.

We account for uncertainty in taxes in accordance with authoritative guidance. A reconciliation of the unrecognized tax benefits is as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance, beginning of the year	$22	$45
Increase for tax positions related to the current year	23	36
Decrease for tax positions related to prior years	—	—
Balance, end of year	$45	$81

All of our gross unrecognized tax benefits, if recognized, would affect our effective tax rate. We do not expect or anticipate a significant increase or decrease over the next twelve months in the unrecognized tax benefits reported above. We recognize accrued interest and penalties related to unrecognized tax benefits as a component of income tax expense. As of December 31, 2019 and 2020, we had not accrued any interest or penalties related to unrecognized tax benefits.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Retirement Plan (FY)	12 Months Ended
Retirement Plan (FY)	Dec. 31, 2020
Retirement Plan [Abstract]
Retirement Plan	15. Retirement Plan The Company sponsors various defined contribution retirement plans for its eligible U.S. and non-U.S. employees. Total contributions to these plans were $0.15 million and $0.31 million for the years ended December 31, 2019 and 2020, respectively. For employees in the United States, the Company matches pretax employee contributions up to a maximum of $19,500 per participant per year.

Segment Information (FY)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Segment Reporting [Abstract]

Segment Information

14. Segment Information

The Company has one segment: manufacturing and servicing of Voyager Tracker. The Company’s Chief Executive Officer (the chief operating decision maker) views and evaluates operations, manages resource allocations, and measures performance based on the results of the Company’s reportable operating segment under its management reporting system. The application of this structure permits us to align our strategic business initiatives and corporate goals in a manner that best focuses our businesses and support operations for success.

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
United States	$59,591	$52,984	$143,034	$168,540
Other	49	5	139	264
Total net revenue	$59,640	$52,989	$143,173	$168,804

16. Segment Information

	Years Ended December 31,
	2019	2020
United States	$45,264	$187,093
Vietnam	7,149	38
Other	711	221
Total net revenue	$53,124	$187,352

Other than the United States, no other individual country exceeded 10% or more of total revenue during the year ended December 31, 2020. Other than the United States and Vietnam, no other individual country exceeded 10% or more of total revenue during the year ended December 31, 2019.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

Related Parties (FY)	9 Months Ended	12 Months Ended
Related Parties (FY)	Sep. 30, 2021	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Parties	15. Related Parties On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from founders of the Company. On January 8, 2021, the Company’s Board of Directors approved a share repurchase of 148,440 shares of common stock for an aggregate price of $0 from founders of the Company. On April 5, 2021, the Company’s Board of Directors approved a share repurchase of 717,460 shares of common stock for an aggregate price of $0 from founders of the Company. On June 29, 2021, the Company made a success-based fee payment in the amount of $1.9 million to two Executive Members of Dimension Energy LLC. (See Note. 7)	17. Related Parties On January 30^th, 2017, the Company issued promissory notes worth $7 million, out of which $6.0 million was issued to two Board Members. The notes carry an interest rate of 5% and expire five years from date of issuance. As described in Note 8, the Company repaid the principal during the year ended December 31, 2020. For the years ended December 31, 2019 and 2020 the Company incurred interest expense of $0.3 million and $0.2 million related to the notes issued to the related parties, respectively. In combination with the note, the Company also issued 25,000 pre-split shares of common stocks for every $250,000 of notes purchased by such investors. On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from a founder of the Company. The repurchase of these shares is recorded as treasury stock on the Company’s consolidated balance sheet as of December 31, 2020. Transactions with the Company’s unconsolidated subsidiary Dimension Energy LLC for the years ended December 31, 2019 and 2020 are disclosed in Note 6. There were no other material related-party transactions during the years ended December 31, 2019 and 2020.

Subsequent Events (FY)	12 Months Ended
Subsequent Events (FY)	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	18. Subsequent Events Management evaluates events occurring subsequent to the date of the consolidated financial statements in determining the accounting or disclosure of transactions and events that affect the consolidated financial statements. Subsequent events have been evaluated through March 9, 2021, which is the date that the consolidated financial statements were issued. On January 20, 2021, the Company received notification from the Small Business Administration that they approved the forgiveness of the full $0.8 million Paycheck Protection Plan loan. The Company is monitoring the recent global health emergency driven by the potential impact of the COVID-19 virus, along with global supply and demand dynamics. The extent to which these events may impact the Company’s business will depend on future developments, which are highly uncertain and cannot be predicted at this time. The Company has thus far avoided significant impact to performance of operations, and management will continue to monitor the impact of the global situation on its financial condition, liquidity, operations, suppliers, industry, and workforce.

Subsequent Events (Unaudited) (FY)	12 Months Ended
Subsequent Events (Unaudited) (FY)	Dec. 31, 2020
Subsequent Events (Unaudited) [Abstract]
Subsequent Events (Unaudited)	19. Subsequent Events (Unaudited) The following events occurred subsequent to original issuance of the consolidated financial statements. On April 21, 2021, FCX Solar, LLC (“FCX”), filed a lawsuit against us in the United States District Court for the Southern District of New York. The complaint alleges breach of contract and other claims related to a patent license agreement and consulting relationship between FCX and us. FCX seeks damages of approximately $133 million in the claim. The Company believes we have strong defenses to the claim, and we plan to vigorously defend against it. The Company and its management considered (a) the facts described above, (b) the preliminary stage of the proceeding and (c) the advice of outside legal counsel on the claims, and determined that it is not probable that FCX will prevail on the merits, and continues to believe that the Company’s likelihood of material loss is remote.

Description of Business (Q3)	9 Months Ended	12 Months Ended
Description of Business (Q3)	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. Description of Business FTC Solar, Inc. (the “Company”, “we”, “our”, or “us”) was founded in 2017 and is incorporated in the state of Delaware. We are a global provider of advanced solar tracker systems, supported by proprietary software and value-added engineering services. Our mission is to provide differentiated products, software and services that maximize energy generation and cost savings for our customers, and to help facilitate the continued growth and adoption of solar power globally. Trackers significantly increase the amount of solar energy produced at a solar installation by moving solar panels throughout the day to maintain an optimal orientation relative to the sun. Our tracker systems are currently marketed under the Voyager brand name (“Voyager Tracker” or “Voyager”). Voyager is a next-generation two-panel in-portrait single-axis tracker solution that we believe offers industry-leading performance and ease of installation. We are a team of dedicated renewable energy professionals focused on delivering cost reductions to our clients across the solar project development and construction cycle. With significant US and worldwide project installation experience, our differentiated offerings drive value for solar solutions spanning a range of applications including ground mount, tracker, canopy, and rooftop. The Company is headquartered in Austin, Texas and has subsidiaries in Australia, India, Singapore, and South Africa. Initial Public Offering and Related Transaction The Company’s common stock began trading on the Nasdaq Stock Exchange on April 28, 2021, under the symbol “FTCI” and on April 30, 2021, the Company completed its Initial Public Offering (“IPO”). In connection with the IPO, the Company issued and sold 19,840,000 shares of its common stock at a public offering price of $13.00 per share. Prior to the completion of the IPO, the Board of Directors and Stockholders approved an approximately 8.25-for-1 forward stock split (the “Forward Stock Split”) of the Company’s shares of common stock which became effective on April 28, 2021. The Company received aggregate proceeds of $241.2 million from the IPO, net of the underwriting discount and commissions and before offering costs and used $54.2 million to purchase and retire an aggregate of 4,455,384 shares of our common stock, some of which resulted from the settlement of certain vested Restricted Stock Units (“RSUs”) and the exercise of certain options in connection with the IPO at the IPO price less underwriting discounts and commissions Offering costs, including legal, accounting, printing and other IPO-related costs, were reclassified to Additional paid-in capital and recorded against the proceeds from the offering during the quarter ended June 30, 2021. JOBS Act Accounting Election We are an emerging growth company, as defined in the Jumpstart Our Business Startups (JOBS) Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards until such time as those standards apply to private companies. Accordingly, we have elected to use the extended transition period to adopt new or revised accounting standards.	1. Description of Business FTC Solar, Inc. (the “Company”, “we”, “our”, or “us”) was founded in 2017 and is incorporated in the state of Delaware. The Company is a team of dedicated renewable energy professionals focused on delivering cost reductions to our clients across the solar project development and construction cycle. With significant US and worldwide project installation experience, our differentiated offerings drive value for solar solutions spanning a range of applications including ground mount, tracker, canopy, and rooftop. The Company is headquartered in Austin, Texas and has subsidiaries in Australia, India, and Singapore. On January 13, 2017, the Company entered into an asset purchase agreement with SunEdison Utility Holdings, Inc. (“Seller”) to purchase all assets of the Seller, in addition to assuming any liabilities, for a total transaction price of $6 million. SunEdison discontinued its operations and filed for bankruptcy prior to the acquisition date. The assets purchased as part of this acquisition were spun off from SunEdison. As a result of the acquisition, the Company acquired intangible assets in the form of developed technology (AP90 Tracker) and software, and inventory. In connection with the acquisition, the Company was formed in 2017 by the management team behind the AP90 tracker, a first-generation tracker based on a one-panel in-portrait, linked-row design. The management team utilized their design and construction experience, and their experience with installing and operating other competitive tracking solutions, to create the next-generation Voyager Tracker, which achieved product certification in 2019.

Revision of Previously Issued Financial Statements (Q3)

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Revision of Previously Issued Financial Statements

2. Revision of Previously Issued Financial Statements

Background of the Revision

In connection with the preparation of the Company’s financial statements as of and for the three months ended September 30, 2021, the Company identified an error in the basic and diluted earnings per share (“EPS”) calculation for the three and six months ended June 30, 2021. Specifically, the Company incorrectly omitted from the basic and diluted weighted-average shares outstanding calculation shares of common stock underlying RSUs that became fully vested during the period but had not yet been settled through the legal issuance of common stock. Additionally, the Company identified that it overstated stock-based compensation expense by $3.5 million for the three and six months ended June 30, 2021 due to an error in the calculation of expense related to grantees’ RSU awards. Although the

Company has concluded that these errors are immaterial to the previously issued interim financial statements, the Company is correcting these errors by revising the previously issued unaudited condensed consolidated financial statements as of June 30, 2021 and for the three and six months ended June 30, 2021.

Effect of the Revision

The following table summarizes the effect of the revision on the affected financial statement line items within the previously reported unaudited condensed consolidated financial statements as of the date, and for the periods indicated. The errors had no impact on total cash flows for operating, investing, or financing activities, but did impact line items in the indirect method of operating cash flow presentation as shown below:

	As of and for Three Months Ended June 30, 2021 (As Previously Reported)	Adjustments	As of and for Three Months Ended June 30, 2021 (As Revised)
	(in thousands, except share and per share data)
Condensed Consolidated Balance Sheet
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue - Product	$43,885	$(7)	$43,878
Research and development	5,585	(2)	5,583
Selling and Marketing	3,258	(161)	3,097
General and administrative	51,063	(3,321)	47,742
Total operating expenses	59,906	(3,484)	56,422
Loss from operations	(75,963)	3,491	(72,472)
Loss before income taxes	(55,590)	3,491	(52,099)
Net loss	(55,841)	3,491	(52,350)
Comprehensive loss	(55,834)	3,491	(52,343)
Net loss per share - basic	(0.70)	0.09	(0.61)
Net loss per share - diluted	(0.70)	0.09	(0.61)
Weighted-average common shares outstanding-basic	79,229,174	6,927,135	86,156,309
Weighted-average common shares outstanding - diluted	79,229,174	6,927,135	86,156,309
Condensed Consolidated Statement of Stockholders’ Equity
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Net loss	(55,841)	3,491	(52,350)
Stock-based compensation	56,192	(3,491)	52,701
Note 11. Net loss per share
Net loss	$(55,841)	$3,491	$(52,350)
Basic weighted-average number of common shares outstanding	79,229,174	6,927,135	86,156,309
Diluted weighted-average number of common shares outstanding	79,229,174	6,927,135	86,156,309
Basic loss per share	(0.70)	0.09	(0.61)
Diluted loss per share	(0.70)	0.09	(0.61)

	As of and for Six Months Ended June 30, 2021 (As Previously Reported)	Adjustments	As of and for Six Months Ended June 30, 2021 (As Revised)
	(in thousands, except share and per share data)
Condensed Consolidated Balance Sheet
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue - Product	$98,881	$(7)	$98,874
Research and development	7,539	(2)	7,537
Selling and Marketing	4,358	(161)	4,197
General and administrative	56,147	(3,321)	52,826
Total operating expenses	68,044	(3,484)	64,560
Loss from operations	(83,982)	3,491	(80,491)
Loss before income taxes	(62,833)	3,491	(59,342)
Net loss	(63,283)	3,491	(59,792)
Comprehensive loss	(63,277)	3,491	(59,786)
Net loss per share - basic	(0.87)	0.09	(0.78)
Net loss per share - diluted	(0.87)	0.09	(0.78)
Weighted-average common shares outstanding - basic	73,106,935	3,474,582	76,581,517
Weighted-average common shares outstanding - diluted	73,106,935	3,474,582	76,581,517
Condensed Consolidated Statement of Cash Flows
Net loss	$ (63,283)	$ 3,491	$ (59,792)
Stock-based compensation	56,641	(3,491)	53,150
Note 11. Net loss per share
Net loss	$ (63,283)	$ 3,491	$ (59,792)
Basic weighted-average number of common shares outstanding	73,106,935	3,474,582	76,581,517
Diluted weighted-average number of common shares outstanding	73,106,935	3,474,582	76,581,517
Basic loss per share	(0.87)	0.09	(0.78)
Diluted loss per share	(0.87)	0.09	(0.78)
Shares of common stock issuable upon vesting of restricted stock awards	15,079	(9,885)	5,194
Potential common shares excluded from diluted net loss per share	23,231	(9,885)	13,346

Summary of Significant Accounting Policies (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

Forward Stock Split

Use of Estimates

COVID-19 Pandemic

Unaudited Interim Financial Information

Concentration of Credit Risk

Equity Method Investments

Stock -Based Compensation

Revenue Recognition

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

The revenue for shipping and handling services is recognized over-time based on shipping terms of the arrangements, as this faithfully depicts the Company’s performance in transferring control.

Term-based software license revenue

Subscription and Maintenance and support services revenue

Cost of Revenue

Warranty

Remaining Performance Obligations

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

New Accounting Pronouncements Not Yet Adopted

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

Forward Stock Split

Reclassification

Liquidity

Use of Estimates

COVID-19 Impact

Functional Currency

Cash

As of December 31, 2019 and 2020, the Company had $7.2 million and $32.4 million in cash, respectively.

As of December 31, 2019 and 2020, the Company had $1.0 million in restricted cash. The restricted cash represents cash collateral posted with providers of letters of credit.

Concentrations of Credit Risk

The Company’s accounts receivables are derived from revenue earned from customers primarily located in the United States of America and Asia Pacific.

Equity Method Investments

The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Consolidated Statement of Operations. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions.

Fair Value of Financial Instruments

The fair value hierarchy prioritizes the inputs into three broad levels:

•	Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities.

•

•	Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company did not hold any financial instruments measured at fair value on a recurring basis categorized within the fair value hierarchy at December 31, 2019 and 2020.

Inventories

Leases

Property and Equipment

Capitalized Software

Long Lived Assets

Revenue Recognition

Revenues from Contract with Customers

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

Term-based software license revenue

Term-based software license revenue included under product revenue is primarily derived from sale of term-based software licenses that are deployed on the customers’ own servers and has significant standalone functionality. The revenue is recognized upon transfer of control to the customer. The control for term-based software license is transferred at the later of delivery to the customer or the software license start date. Term-based software license revenue is immaterial for years ended December 31, 2019 and 2020.

Subscription and Maintenance and support services revenue

Subscription revenue is derived from a subscription-based enterprise licensing model with contract terms typically ranging from one to two years and consists of subscription fees from the licensing of Subscription services. Subscription services revenue is immaterial for years ended December 31, 2019 and 2020. The hosted on-demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Services revenue includes maintenance and support service revenue related to term-based software licenses. Support revenue is derived from ongoing security updates, upgrades, bug fixes, and maintenance. A time-elapsed method is used to measure progress because the Company transfers control evenly over the contractual period. Accordingly, the fixed consideration related to these revenues is generally recognized on a straight-line basis over the contract term beginning on the date access is provided.

Contract liabilities

Cost of Revenue

Cost of revenue consists primarily of costs related to raw materials, freight and delivery, product warranty, and personnel costs (salaries, bonuses, benefits, and stock-based compensation). Personnel costs in cost of revenue includes both direct labor costs as well as costs attributable to any individuals whose activities relate to the procurement, installment and delivery of the finished product and services. Deferred cost of revenue results from the timing differences between the costs incurred in advance of the satisfaction of all revenue recognition criteria consistent with our revenue recognition policy.

Advertising Costs

Research and Development Expenses

Warranty

Accounts Receivable and Allowance for Doubtful Debts

Stock-Based Compensation

The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.

Income Taxes

The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes.

Deferred Offering Costs

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

New Accounting Pronouncements Not Yet Adopted

Revenue (Q3)	9 Months Ended	12 Months Ended
Revenue (Q3)	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	4. Revenue The Company’s product revenue and service revenue is presented in the Condensed Consolidated Statement of Comprehensive Loss. Revenue by geographic region is based on the customer’s location and presented under Note 14. Unbilled revenue and contract liabilities The timing of revenue recognition, billing, and cash collection results in the recognition of accounts receivable, unbilled receivables, and deferred revenue in the Condensed Consolidated Balance Sheets. Unbilled receivables represent an unconditional right to consideration before customers are invoiced. Unbilled receivables are recorded within accounts receivable on the Condensed Consolidated Balance Sheets at the end of the reporting period and consist of $1.2 million and $15.7 million as of December 31, 2020 and September 30, 2021, respectively. The Company’s contracts have a varied range of terms based on the type of products and services sold. Deferred revenue amounts to $23.0 million and $9.6 million as of December 31, 2020 and September 30, 2021, respectively, consisting of customer deposits related to products and services which were billed in advance. The Company expects to recognize 100% of the revenue related to deferred revenue within the next 12 months. During the nine months ended September 30, 2020 and 2021, the Company recognized $19.9 million and $23.0 million, respectively from deferred revenue recorded at December 31, 2019 and 2020.	3. Revenue The Company’s product revenue and service revenue is presented in the consolidated statements of operations. Revenue by geographic region is based on the customer’s location and presented under Note 16. Transaction Price Allocated to the Remaining Performance Obligations The Company’s contracts have a varied range of terms based on the type of products and services sold. As of December 31, 2019 and 2020, the aggregate amount of the transaction price allocated to remaining performance obligations was $19.9 million and $23.0 million, respectively. The Company expects to recognize 100% of the revenue related to remaining performance obligations in the 12 months following year end.

- Definition

+ References

+ Details

Prepaid Expenses and Other Current Assets (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Prepaid Expense and Other Assets, Current [Abstract]

Prepaid Expenses and Other Current Assets

5. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31, 2020	September 30, 2021
Vendor deposits	$4,205	$18,125
Prepaid expenses	1,043	4,060
Deferred cost of revenue	992	—
Surety collateral	113	246
Other current assets	571	1,127
	$6,924	$23,558

5. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	As of December 31,
	2019	2020
Vendor deposits	$1,738	$4,205
Prepaid expenses	209	1,043
Deferred cost of revenue	19	992
Surety collateral^*	1,835	113
Other current assets	47	571
	$3,848	$6,924

*	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Accrued Expenses and Other Current Liabilities (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accrued Expenses and Other Current Liabilities Abstract

Accrued Expenses and Other Current Liabilities

6. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	December 31, 2020	September 30, 2021
Accrued cost of revenue	$ 7,812	$33,279
Accrued expenses	2,856	3,205
Warranty reserves	3,985	1,183
Accrued compensation	2,869	1,766
Accrued interest expense	28	128
Other	945	685
Total	$18,495	$40,246

4. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2019	2020
Accrued cost of revenue	$2,106	$ 7,812
Accrued expenses	1,644	2,856
Warranty reserves	1,368	3,985
Accrued compensation	177	2,869
Accrued interest expense	47	28
Other	33	945
Total	$5,375	$18,495

Sales of Equity Method Investments (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Equity Method Investments and Joint Ventures [Abstract]

Sale of Equity Method Investments

7. Sale of Equity Method Investments

During the three months ended September 30, 2021, the Company received a $0.2 million escrow release payment and recognized the income in accordance with our policy election.

6. Equity Method Investments

Equity method investments are as follows (in thousands, except percentages):

Summarized financial information for the Company’s equity method investment is as follows:

Balance sheet (in thousands)

	As of December 31,
	2019	2020
Current assets	$4,466	$10,162
Non-current assets	13,123	9,045
Current liabilities	3,219	12,350
Non-current liabilities	14,344	9,723
Members’ equity (deficit)	25	(2,866)

Statement of operations (in thousands)

	Years Ended December 31
	2019	2020
Revenue	$—	$22,570
Gross profit	—	17,360
Income (loss) from operations	(3,413)	9,185
Net income (loss)	(2,987)	5,933
Share of earnings from equity method investment	(709)	1,399

Debt and Other Borrowings (Q3)	9 Months Ended	12 Months Ended
Debt and Other Borrowings (Q3)	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt and Other Borrowings	8. Debt and Other Borrowings On January 30, 2017, the Company sold $7.0 million in aggregate principal amount of secured five-year promissory notes (“the Notes”) through a private placement. Pursuant to the issuance of the Notes, the Company issued 25,000 shares of common stock for every $250,000 of Notes purchased. The fair value of common stock issued was accounted for as debt discount and was amortized over the term of the Notes. The Notes had a fixed rate of 5% per annum payable at maturity. The Company repaid the principal during the year ended December 31, 2020. On June 17, 2019, the Company entered into a revolving line of credit agreement with the Western Alliance Bank for a total principal amount of $1.0 million and maturity in two years from the date of borrowing. The line of credit had a variable rate of interest, based on movement of prime rate as calculated and published by the Wall Street Journal and required the Company to pay regular monthly payments of all interest accrued as of each payment date. The prime rate at the time of borrowing was at 5.50% per annum. The outstanding balance for the revolving line of credit as of December 31, 2020 was $1 million. The outstanding balance was paid in full and the revolving credit line was closed as of March 31, 2021. On April 30, 2020, the Company received a Paycheck Protection Program (“PPP”) loan pursuant to the Coronavirus Aid, Relief, and Economic Security Act (the “CARES” Act) in the amount of $0.8 million. The PPP loan had a two-year term and bore a fixed interest rate of 1%. Under the terms of the CARES act, the PPP loan was eligible to be forgiven, in part or whole, if the proceeds were used to retain and pay employees and for other qualifying expenditures. On January 20, 2021, the Company received notification from the Small Business Administration that they approved the forgiveness of the full $0.8 million PPP loan. The Company recorded the forgiveness of the PPP loan as a gain on debt extinguishment in other income. On April 30, 2021, the Company entered into a $100 million senior secured revolving credit facility, by and among the Company, as borrower, the several financial institutions from time-to-time parties thereto, and Barclays Bank PLC, as an issuing lender, the swingline lender and as administrative agent (the “Credit Agreement”). The Credit Agreement has an initial three-year term, and it will be used for working capital and for other general corporate purposes. The Company has not made any draws on the revolving credit facility. The Credit Agreement includes the following terms: (i) aggregate commitments of up to $100 million, with letter of credit and swingline sub-limits; (ii) customary base rate of LIBOR plus 3.25% per annum, respectively; (iii) initial commitment fees of 0.50% per annum; (iv) initial letter of credit fees of 3.25% per annum; and (v) other customary terms for a corporate revolving credit facility. The facility is secured by a first priority lien on substantially all of the Company’s assets, subject to certain exclusions, and customary guarantees. The Credit Agreement includes the following financial condition covenants that the Company is required to satisfy: (i) maintain a minimum liquidity of $125 million for each quarter; (ii) maintain a 3.75 times leverage ratio; and (iii) maintain a 1.5 times interest coverage ratio. The leverage and interest coverage ratios will be triggered when the Company achieves $50 million in adjusted EBITDA over a trailing twelve months. Once the leverage and interest coverage ratios are triggered the minimum liquidity will not have a minimum limit. Minimum liquidity includes unrestricted cash plus the undrawn balance of the revolving credit facility. The minimum liquidity covenant was the only financial condition covenant the Company had to satisfy as of the period ended September 30, 2021. As of September 30, 2021, the Company was in full compliance with its financial condition covenant. The Company added $2.1 million in debt issuance costs related to the revolving credit facility which were included in other assets in the Condensed Consolidated Balance Sheets. The debt issuance costs are being amortized over a three-year initial term of the loan. As of September 30, 2021 the unamortized debt issuance costs amounted to $1.8 million. Included in interest expense for the three and nine months periods ended September 30, 2021 are credit facility revolver fees and amortization of debt issuance costs. The Company had $0.1 million in revolver fees and $0.2 million in amortized debt issuance cost for the three months ended September 30, 2021 and $0.2 million in revolver fees and $0.3 million in amortized debt issuance cost for the nine months ended September 30, 2021, respectively. The Company recognized $0.1 million and $0.3 million of interest expense on its debt and other borrowings for the three months ended September 30, 2020 and 2021 and $0.3 million and $0.5 million for the nine months ended September 30, 2020 and 2021, respectively.	8. Debt and Other Borrowings On January 30, 2017, the Company sold $7.0 million in aggregate principal amount of secured five-year promissory notes (“the notes”) through a private placement. Pursuant to the issuance of the promissory notes, the Company issued 25,000 pre-split shares of common stock for every $250,000 of notes purchased. The fair value of common stock issued was accounted for as debt discount and was amortized over the term of the note. The notes bear a fixed rate of 5% per annum payable at maturity. The Company repaid the principal during the year ended December 31, 2020 and recorded a loss on debt extinguishment of $0.1 million in interest expense, net in the Consolidated Statement of Operations. On June 17, 2019, the Company entered into a revolving line of credit agreement with the Western Alliance Bank for a total principal amount of $1.0 million and maturity in two years from the date of borrowing. The line of credit bears a variable rate of interest, based on movement of prime rate as calculated and published by the Wall Street Journal. The Company will pay the regular monthly payments of all interest accrued as of each payment date. The prime rate at the time of borrowing was at 5.50% per annum. As of December 31, 2019 and 2020, the outstanding balance for the revolving line of credit was $1.0 million, payable on June 10, 2021. On April 30, 2020, the Company received a Paycheck Protection Program (“PPP”) loan pursuant to the Coronavirus Aid, Relief, and Economic Security Act (the “CARES” Act) in the amount of $0.8 million. The loan had a two-year term and bore a fixed interest rate of 1%. Under the terms of the CARES act the loan was eligible to be forgiven, in part or whole, if the proceeds were used to retain and pay employees and for other qualifying expenditures. On January 20, 2021, the Company received notification from the Small Business Administration that they approved the forgiveness of the full $0.8 million PPP loan. The Company recognized $0.5 million and $0.5 million interest expense on its debt and other borrowings for the years ended December 31, 2019 and 2020, respectively. The notes and revolving line of credit contain affirmative customary covenants, including maintenance of insurance, notices of claims and litigations, subordination of other lender’s credit and compliance with environmental laws. As of December 31, 2019 and 2020, the Company was in compliance with all required covenants.

- Definition

+ References

+ Details

Commitments and Contingencies (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Litigation

The Company has not recorded any material loss contingency in the Condensed Consolidated Balance Sheets as of December 31, 2020 and September 30, 2021.

Warranties

Changes in the Company’s product warranty reserves were as follows (in thousands):

			September 30, 2021
Balance at beginning of period, December 31, 2020			$ 6,811
Warranties issued during the period			2,902
Settlements made during the period			(3,507)
Changes in liability for pre-existing warranties			(783)
Balance at end of period			$ 5,423

9. Commitments and Contingencies

Litigation

Warranties

The Company provides standard warranties on its hardware products. The liability amount is based on actual historical warranty spending activity by type of product, customer, and geographic region, modified for any known differences such as the impact of reliability improvements. As of December 31, 2019 and 2020, warranty reserves totaling $1.4 million and $4.0 million were recorded in accrued expenses and other current liabilities, respectively and $0.7 million and $2.8 million and were recorded in other non-current liabilities, respectively, in the Company’s Consolidated Balance Sheets.

Changes in the Company’s product warranty reserves were as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance at beginning of period	$ —	$ 2,057
Warranties issued during the period	2,057	7,866
Settlements made during the period	—	(3,111)
Changes in liability for pre-existing warranties	—	(1)
Balance at end of period	$2,057	$ 6,811

Stock-Based Compensation (Q3)	9 Months Ended
Stock-Based Compensation (Q3)	Sep. 30, 2021
Stock Plans [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation On April 30, 2021, in connection with the IPO offering, the Company used $54.2 million of net proceeds from the IPO to purchase and retire an aggregate of 4,455,384 shares of our common stock, of which 2,191,557 was a repurchase of common shares and 2,263,827 shares were from the settlement of certain vested RSUs and common shares exercised from options in connection with the IPO offering, at the initial public offering price net of underwriters’ fees and commissions. The Company’s stock-based compensation expense for the three and nine months ended September 30, 2021 was $5.4 million and $58.5 million, an increase of $5.0 million and $57.1 million when compared to stock-based compensation expense for the three and nine months ended September 30, 2020, respectively. The increases have been primarily due to RSUs, for which the service-based vesting condition was satisfied and for which the liquidity event performance vesting condition was met in connection with our IPO. We utilized a graded vesting method which results in an accelerated recognition of compensation costs. Stock-based compensation expense incurred was $0.4 million and $5.4 million for the three months ended September 30, 2020 and 2021 and $1.4 million and $58.5 million for the nine months ended September 30, 2020 and 2021, respectively.

Stockholders' Equity (Q3)	9 Months Ended
Stockholders' Equity (Q3)	Sep. 30, 2021
Equity [Abstract]
Common Stock	11. Stockholders’ Equity Preferred Stock The Certificate of Incorporation, as amended as of April 28, 2021, and amended as of June 7, 2021, (the “Certificate of Incorporation”), authorizes the Company to issue 10 million shares of Preferred Stock with a par value of $0.0001 with such designation, rights and preferences as may be determined from time to time by the Company’s board of directors. As of September 30, 2021 there were no shares of preferred stock issued or outstanding. Common Stock The Certificate of Incorporation authorizes the Company to issue 850 million shares of $0.0001 par value of Common Stock. Holders of Common Stock are entitled to dividends, as and when, declared by the Board of Directors, subject to the rights of the holders of all classes of stock outstanding having priority rights as to dividends. There have been no dividends declared to date. The holders of the Common Stock are entitled to one vote for each share of Common Stock; provided that, except as otherwise required by law, holders of Common Stock (in such capacity) shall not be entitled to vote on any amendment to the Certificate of Incorporation that relates solely to the terms of one or more outstanding series of Preferred Stock if the holders of such affected series are entitled, either separately or together with the holders of one or more other such series, to vote thereon pursuant to the Certificate of Incorporation. In March 2020, the Company sold 9,162,976 shares of common stock at $3.27 per share for an aggregate purchase price of $30.0 million. The proceeds are available for working capital and other corporate purposes. On April 30, 2021, the Company closed on its IPO in which we issued and sold 19,840,000 shares of our common stock at a public offering price of $13.00 per share. We received aggregate proceeds of $241.2 million from the IPO, net of approximately $16.8 million in underwriting discount and commissions and before offering costs. The Company used $54.2 million of net proceeds from the IPO to purchase and retire an aggregate of 4,455,384 shares of our common stock, of which 2,191,557 was a repurchase of common shares and 2,263,827 shares were from the settlement of certain vested RSUs and common shares exercised from options in connection with the IPO offering. The Company is using the proceeds from the IPO for general corporate purposes, including working capital and operating expenses. We may also use a portion of such proceeds to acquire or invest in businesses, products, services or technologies; however, we do not have binding agreements for any material acquisitions or investments at this time though, we would expect to use a portion of such proceeds to provide funding for future development capital in connection with the multi project opportunity for 1.7 gigawatts (“GWs”) of projects using our tracker systems. Treasury Stock On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from founders of the Company. The repurchase of these shares are recorded as treasury stock on the Company’s Condensed Consolidated Balance Sheets as of December 31, 2020 and the shares will be added to the overall pool of stock available to be utilized for future option/stock award issuances to other employees of the organization. On January 8, 2021, the Company’s Board of Directors approved a share repurchase of 148,440 shares of common stock for an aggregate price of $0 from founders of the Company. The repurchase of these shares are recorded as treasury stock on the Company’s Condensed Consolidated Balance Sheets as of the period ended September 30, 2021 and the shares will be added to the overall pool of stock available to be utilized for future option/stock award issuances to other employees of the organization. On April 5, 2021, the Company’s Board of Directors approved a share repurchase of 717,460 shares of common stock for an aggregate price of $0 from founders of the Company. The repurchase of these shares are recorded as treasury stock on the Company’s Consolidated Balance Sheets as of the period ended September 30, 2021 and the shares will be added to the overall pool of stock available to be utilized for future option/stock award issuances to other employees of the organization.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI http://asc.fasb.org/topic&trid=2208762

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Net Loss Per Share (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Net Loss Per Share [Abstract]

Net Loss Per Share

12. Net loss per share

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
Basic and diluted:
Net loss	$ (2,840)	$ (22,916)	$ (6,196)	$ (82,707)
Basic weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Diluted weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Basic loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)
Diluted loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)

	As of September 30,
	2020	2021
Shares of common stock issuable under stock option plans outstanding	8,566	9,610
Shares of common stock issuable upon vesting of restricted stock awards	13,622	5,598
Potential common shares excluded from diluted net loss per share	22,188	15,208

13. Net loss per share

The table below sets forth the computation of basic and diluted loss per share (in thousands, except per share amounts):

	Years Ended December 31,
	2019	2020
Basic and diluted:
Net loss	$(13,495)	$(15,924)
Weighted-average number of common shares outstanding	62,043	68,811
Basic and diluted loss per share	$(0.22)	$(0.23)

	As of December 31,
	2019	2020
Shares of common stock issuable under stock option plans outstanding	8,082	8,525
Shares of common stock issuable upon vesting of restricted stock awards	5,249	14,122
Potential common shares excluded from diluted net loss per share	13,331	22,647

Income Taxes (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

14. Income Taxes

The following table summarizes our U.S. and foreign income (loss) before income taxes (in thousands):

	Years Ended December 31,
	2019	2020
U.S.	$(13,534)	$(16,269)
Foreign	—	262
Total loss before income taxes	$(13,534)	$(16,007)

	Years Ended December 31,
	2019	2020
Current
Federal	$—	$(159)
State	(37)	1
Foreign	—	78
Deferred
Federal	(2)	(3)
State	—	—
Total income tax expense/(benefit)	$(39)	$(83)

	Years Ended December 31,
	2019	2020
Income tax expense (benefit) derived by applying the federal statutory tax rate to income (loss) before income taxes	$(2,842)	$(3,362)
State taxes, net of federal	(551)	(215)
Research and experimentation tax credit	(118)	(179)
Valuation allowance	3,184	3,523
Stock compensation	225	406
Dividends received deduction	—	(308)
Permanent differences and other	63	52
	$(39)	$(83)

	As of December 31,
	2019	2020
Deferred tax assets:
Fixed assets and intangibles	$156	$135
Leases	—	106
Accrued expenses	333	2,066
Net operating loss carryforward	4,626	6,679
Capital loss carryforward	501	—
Investment difference	—	148
R&D credit carryforward	181	325
Subtotal	5,797	9,459
Less valuation allowance	(5,774)	(9,297)
Total deferred tax asset	23	162
Deferred tax (liabilities):
Investment difference	(15)	—
Leases	—	(101)
Prepaid expenses	(11)	(61)
Total deferred tax (liability)	(26)	(162)
Net deferred tax asset (liability)	$(3)	$—

The Company has federal R&D Credit carryforwards of approximately $0.4 million at December 31, 2020, which begin to expire in 2038.

We account for uncertainty in taxes in accordance with authoritative guidance. A reconciliation of the unrecognized tax benefits is as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance, beginning of the year	$22	$45
Increase for tax positions related to the current year	23	36
Decrease for tax positions related to prior years	—	—
Balance, end of year	$45	$81

- Definition

+ References

+ Details

Segment Information (Q3)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Segment Reporting [Abstract]

Segment Information

14. Segment Information

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
United States	$59,591	$52,984	$143,034	$168,540
Other	49	5	139	264
Total net revenue	$59,640	$52,989	$143,173	$168,804

16. Segment Information

	Years Ended December 31,
	2019	2020
United States	$45,264	$187,093
Vietnam	7,149	38
Other	711	221
Total net revenue	$53,124	$187,352

- Definition

+ References

+ Details

Related Parties (Q3)	9 Months Ended	12 Months Ended
Related Parties (Q3)	Sep. 30, 2021	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Parties	15. Related Parties On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from founders of the Company. On January 8, 2021, the Company’s Board of Directors approved a share repurchase of 148,440 shares of common stock for an aggregate price of $0 from founders of the Company. On April 5, 2021, the Company’s Board of Directors approved a share repurchase of 717,460 shares of common stock for an aggregate price of $0 from founders of the Company. On June 29, 2021, the Company made a success-based fee payment in the amount of $1.9 million to two Executive Members of Dimension Energy LLC. (See Note. 7)	17. Related Parties On January 30^th, 2017, the Company issued promissory notes worth $7 million, out of which $6.0 million was issued to two Board Members. The notes carry an interest rate of 5% and expire five years from date of issuance. As described in Note 8, the Company repaid the principal during the year ended December 31, 2020. For the years ended December 31, 2019 and 2020 the Company incurred interest expense of $0.3 million and $0.2 million related to the notes issued to the related parties, respectively. In combination with the note, the Company also issued 25,000 pre-split shares of common stocks for every $250,000 of notes purchased by such investors. On July 21, 2020, the Company’s Board of Directors approved a share repurchase of 9,896,666 shares of common stock for an aggregate price of $0 from a founder of the Company. The repurchase of these shares is recorded as treasury stock on the Company’s consolidated balance sheet as of December 31, 2020. Transactions with the Company’s unconsolidated subsidiary Dimension Energy LLC for the years ended December 31, 2019 and 2020 are disclosed in Note 6. There were no other material related-party transactions during the years ended December 31, 2019 and 2020.

Summary of Significant Accounting Policies (FY) (Policies)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

COVID-19 Pandemic

COVID-19 Impact

Functional Currency

Cash

As of December 31, 2019 and 2020, the Company had $7.2 million and $32.4 million in cash, respectively.

As of December 31, 2019 and 2020, the Company had $1.0 million in restricted cash. The restricted cash represents cash collateral posted with providers of letters of credit.

Concentration of Credit Risk

Concentrations of Credit Risk

The Company’s accounts receivables are derived from revenue earned from customers primarily located in the United States of America and Asia Pacific.

Equity Method Investments

The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Consolidated Statement of Operations. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions.

Fair Value of Financial Instruments

The fair value hierarchy prioritizes the inputs into three broad levels:

•	Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities.

•

•	Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company did not hold any financial instruments measured at fair value on a recurring basis categorized within the fair value hierarchy at December 31, 2019 and 2020.

Inventories

Leases

Property and Equipment

Capitalized Software

Long Lived Assets

Revenue Recognition

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

The revenue for shipping and handling services is recognized over-time based on shipping terms of the arrangements, as this faithfully depicts the Company’s performance in transferring control.

Term-based software license revenue

Subscription and Maintenance and support services revenue

Cost of Revenue

Warranty

Remaining Performance Obligations

Revenue Recognition

Revenues from Contract with Customers

Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling)

Term-based software license revenue

Term-based software license revenue included under product revenue is primarily derived from sale of term-based software licenses that are deployed on the customers’ own servers and has significant standalone functionality. The revenue is recognized upon transfer of control to the customer. The control for term-based software license is transferred at the later of delivery to the customer or the software license start date. Term-based software license revenue is immaterial for years ended December 31, 2019 and 2020.

Subscription and Maintenance and support services revenue

Subscription revenue is derived from a subscription-based enterprise licensing model with contract terms typically ranging from one to two years and consists of subscription fees from the licensing of Subscription services. Subscription services revenue is immaterial for years ended December 31, 2019 and 2020. The hosted on-demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Services revenue includes maintenance and support service revenue related to term-based software licenses. Support revenue is derived from ongoing security updates, upgrades, bug fixes, and maintenance. A time-elapsed method is used to measure progress because the Company transfers control evenly over the contractual period. Accordingly, the fixed consideration related to these revenues is generally recognized on a straight-line basis over the contract term beginning on the date access is provided.

Contract Liabilities

Contract liabilities

Cost of Revenue

Cost of revenue consists primarily of costs related to raw materials, freight and delivery, product warranty, and personnel costs (salaries, bonuses, benefits, and stock-based compensation). Personnel costs in cost of revenue includes both direct labor costs as well as costs attributable to any individuals whose activities relate to the procurement, installment and delivery of the finished product and services. Deferred cost of revenue results from the timing differences between the costs incurred in advance of the satisfaction of all revenue recognition criteria consistent with our revenue recognition policy.

Advertising Costs

Research and Development Expenses

Warranty

Accounts Receivable and Allowance for Doubtful Debts

Stock-Based Compensation

Stock -Based Compensation

Stock-Based Compensation

The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.

Income Taxes

The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes.

Deferred Offering Costs

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

New Accounting Pronouncements Not Yet Adopted

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

New Accounting Pronouncements Not Yet Adopted

Summary of Significant Accounting Policies (Q3) (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation These unaudited condensed consolidated financial statements include the results of the Company and its wholly owned subsidiaries and have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). Intercompany accounts and transactions have been eliminated upon consolidation.	Basis of Presentation and Principles of Consolidation These Consolidated Financial Statements include the results of the Company and its wholly owned subsidiaries and have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). Intercompany accounts and transactions have been eliminated upon consolidation.
Forward Stock Split	Forward Stock Split On April 28, 2021, we effected an approximately 8.25-for-1 forward split of our issued and outstanding shares of common stock, par value $0.0001 per share. As a result of the Forward Stock Split, one (1) share of common stock issued and outstanding was automatically increased to approximately 8.25 shares of issued and outstanding common stock, without any change in the par value per share. All information related to common stock, stock options, restricted stock awards and earnings per share have been retroactively adjusted to give effect to the Forward Stock Split for all periods presented.	Forward Stock Split On April 28, 2021, we effected an approximately 8.25-for-1 forward split of our issued and outstanding shares of common stock, par value $0.0001 per share. As a result of the Forward Stock Split, one (1) share of common stock issued and outstanding was automatically increased to approximately 8.25 shares of issued and outstanding common stock, without any change in the par value per share. All information related to common stock, stock options, restricted stock awards and earnings per share have been retroactively adjusted to give effect to the Forward Stock Split for all periods presented. This adjustment impacts footnotes 11, 12, 13, and 17. Also on April 28, 2021, the Company amended and restated its certificate of incorporation which increased the number of authorized shares of all classes of stock to 860,000,000, consisting of (i) 850,000,000 shares of Common Stock, par value $0.0001 per share and (ii) 10,000,000 shares of Preferred Stock, par value $0.0001 per share.
Use of Estimates	Use of Estimates The preparation of the Company’s financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis.	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. Estimates are used for calculating the measure of progress of Voyager tracker projects and deriving the standalone selling prices of the individual performance obligations when determining the revenue recognition, allowances for doubtful accounts, useful lives of intangible assets, fair value of investments, warranty liabilities, income taxes and stock-based compensation. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that it believes are reasonable under the circumstances, including assumptions as to future events. Actual results could differ from those estimates.
Covid-19 Pandemic	COVID-19 Pandemic In March 2020, the World Health Organization declared the novel coronavirus 2019 (“COVID-19”) a global pandemic. The COVID-19 pandemic has had and may continue to have an unfavorable impact on certain parts of our business. The broader implications of the COVID-19 pandemic on our business, financial condition and results of operations remain uncertain and will depend on certain developments, including the duration and severity of the COVID-19 pandemic, the impact of virus variants, the rate of vaccinations, the COVID-19 pandemic’s impact on our customers and suppliers and the range of governmental and community reactions to the pandemic. We have experienced delays in production and shipments in the current quarter due to an outbreak of COVID at a supplier site and a quarantine imposed on one of our shipping vessels. Due to the nature of the pandemic, we may continue to experience reduced customer demand in certain parts of our business or constrained supply that could materially and adversely impact our business, financial condition, results of operations, liquidity and cash flows in future periods.	COVID-19 Impact The COVID-19 pandemic has caused, and continues to cause, widespread economic disruption and has impacted the Company in a number of ways, most notably governmental authorities in the United States and around the world have imposed various restrictions designed to slow the pace of the pandemic, including restrictions on travel and other restrictions that prohibit employees from going to work. The Company expects the extent of the impact on its financial and operational results will depend on the duration and severity of the economic disruption caused by the COVID-19 pandemic. The Company considered the impacts of the COVID-19 pandemic on its significant estimates and judgments used in applying its accounting policies. In light of the pandemic, there is a greater degree of uncertainty in applying these judgments and depending on the duration and severity of the pandemic, changes to its estimates and judgments could result in a meaningful impact to its consolidated financial statements in future periods.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying unaudited condensed consolidated financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2020 and 2021, have been prepared in accordance with GAAP for interim financial statements and pursuant to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, all adjustments have been made that are considered necessary for a fair statement of our financial position as of December 31, 2020 and September 30, 2021, our results of operations for the three and nine months ended September 30, 2020 and 2021 and our cash flows for the nine months ended September 30, 2020 and 2021. The condensed consolidated balance sheets as of December 31, 2020 have been derived from the Company’s audited consolidated financial statements. Operating results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. Certain information and disclosures normally included in the notes to annual financial statements prepared in accordance with GAAP have been omitted from these interim financial statements pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s final prospectus (the “IPO Prospectus”) dated as of April 29, 2021, and filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Securities Act”).
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company is exposed to credit risk in the event of default by the financial institutions holding our cash and cash equivalents that are recorded on our balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits its exposure. The Company has not experienced any losses since inception. The carrying amounts of cash and cash equivalents, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items.	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and accounts receivable. The Company maintains its cash accounts with financial institutions where, at times, deposits exceed federal insurance limits. The Company extends credit to customers in the normal course of business. The Company performs credit analyses and monitors the financial health of its customers to reduce credit risk. The Company’s accounts receivables are derived from revenue earned from customers primarily located in the United States of America and Asia Pacific. During the year ended December 31, 2019, three customers accounted for 59%, 21% and 13% of total revenue, respectively. During the year ended December 31, 2020, four customers accounted for 21%, 19%, 10% and 10% of total revenue, respectively. No other customers accounted for more than 10% of total revenues for these periods. As of December 31, 2019, three customers accounted for 49%, 23% and 18% of accounts receivable, respectively. As of December 31, 2020, three customers accounted for 32%, 25% and 14% of accounts receivable, respectively. No other customers accounted for more than 10% of accounts receivable for these periods.
Equity Method Investments	Equity Method Investments The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Condensed Consolidated Statements of Comprehensive Loss. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions. The Company evaluates equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. Factors considered by the Company when reviewing an equity method investment for impairment include the length of time and the extent to which the fair value of the equity method investment has been less than cost, the investee’s financial condition and near-term prospects and the intent and ability to hold the investment for a period of time sufficient to allow for anticipated recovery. An impairment that is other-than temporary is recognized in the period identified. The Company accounts for distributions received from equity method investees under the “nature of the distribution” approach. Under this approach, distributions received from equity method investees are classified on the basis of the nature of the activity or activities of the investee that generated the distribution as either a return on investment (classified as cash inflows from operating activities) or a return of investment (classified as cash inflows from investing activities). The Company has made an accounting policy election, as a result of disposing of its equity method investment on June 24, 2021, to account for the contingent gains from the earnout provision and projects escrow release only when those amounts become realizable in the periods subsequent to the disposal date. (See Note 7).	Equity Method Investments The Company uses the equity method of accounting for equity investments if the investment provides the ability to exercise significant influence, but not control, over operating and financial policies of the investee. The Company’s proportionate share of the net income or loss of these investees is included in our Consolidated Statement of Operations. Judgment regarding the level of influence over each equity method investment includes considering key factors such as the Company’s ownership interest, legal form of the investee, representation on the board of directors, participation in policy-making decisions and material intra-entity transactions. The Company evaluates equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. Factors considered by the Company when reviewing an equity method investment for impairment include the length of time and the extent to which the fair value of the equity method investment has been less than cost, the investee’s financial condition and near-term prospects and the intent and ability to hold the investment for a period of time sufficient to allow for anticipated recovery. An impairment that is other-than temporary is recognized in the period identified. The Company accounts for distributions received from equity method investees under the “nature of the distribution” approach. Under this approach, distributions received from equity method investees are classified on the basis of the nature of the activity or activities of the investee that generated the distribution as either a return on investment (classified as cash inflows from operating activities) or a return of investment (classified as cash inflows from investing activities).
Stock-Based Compensation	Stock -Based Compensation The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards, stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.	Stock-Based Compensation The Company recognizes compensation expense for all share-based payment awards made, including stock options and restricted stock, based on the estimated fair value of the award on the grant date, in the accompanying consolidated statements of operations over the requisite service period of the awards. The Company calculates the fair value of stock options using the Black-Scholes Option-Pricing model. The fair value of restricted stock grants represents the estimated fair value of the Company’s common stock on the date of grant. The Company accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized using the straight-line attribution approach over the requisite service period. For performance-based awards stock-based compensation is recognized based on graded vesting over the requisite service period when the performance condition is probable of being achieved.
Revenue Recognition	Revenue Recognition The Company derives its revenue primarily from sale of: (1) Voyager Tracker and customized components of Voyager Tracker, (2) individual parts of Voyager Tracker for certain specific transactions, (3) shipping and handling services, (4) term-based software licenses, (5) maintenance and support services for the term-based software licenses, and (6) subscription services. Product revenue includes revenue from Voyager Tracker and customized components of Voyager Tracker, individual part sales for certain specific transactions, and sale of term-based software licenses. Service revenue includes revenue from shipping and handling services, subscription-based enterprise licensing model, and maintenance and support services in connection with the term-based software licenses. Voyager Tracker and individual parts of Voyager Tracker (including shipping and handling) The Company contracts with customers for sale of Voyager Trackers under two different types of arrangements: (1) Purchase Agreements and Equipment Supply Contracts (“Purchase Agreements”) and (2) sale of individual parts of the Voyager Tracker. The Company’s Purchase Agreements typically include two performance obligations- (1) Voyager Tracker or customized components of Voyager Tracker and (2) shipping and handling services. The deliverables included as part of the Voyager Tracker are predominantly accounted for as one performance obligation, as these deliverables are part of a combined promise to deliver a project. Voyager Tracker and customized components of Voyager Tracker performance obligations in the contract are satisfied over-time as work progresses for its custom assembled Voyager Tracker, utilizing an input measure of progress determined by cost-to-cost measures on these projects as this faithfully depicts the Company’s performance in transferring control. The revenue for shipping and handling services is recognized over-time based on shipping terms of the arrangements, as this faithfully depicts the Company’s performance in transferring control. The Company’s sale of individual parts of Voyager Tracker for certain specific transactions include multiple performance obligations consisting of individual parts of the Voyager Tracker. Revenue recognized for the Company’s part sales are recorded at a point in time and recognized when obligations under the terms of the contract with our customer are satisfied. Generally, this occurs with the transfer of control of the asset, which is in line with shipping terms. Term-based software license revenue Term-based software license revenue included under product revenue is primarily derived from sale of term-based software licenses that are deployed on the customers’ own servers and have significant standalone functionality. The revenue is recognized upon transfer of control to the customer. The control for term-based software licenses is transferred at the later of delivery to the customer or the software license start date. Term-based software license revenue is immaterial for the three and nine month periods ended September 30, 2020 and September 30, 2021. Subscription and Maintenance and support services revenue Subscription revenue is derived from a subscription-based enterprise licensing model with contract terms typically ranging from one to two years and consists of subscription fees from the licensing of Subscription services. Subscription services revenue is immaterial for the three and nine month periods ended September 30, 2020 and September 30, 2021. The hosted on-demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Services revenue includes maintenance and support activities related to term-based software licenses. Support revenue is derived from ongoing security updates, upgrades, bug fixes, and maintenance. A time-elapsed method is used to measure progress because the Company transfers control evenly over the contractual period. Accordingly, the fixed consideration related to these revenues is generally recognized on a straight-line basis over the contract term beginning on the date access is provided. Cost of Revenue Cost of revenue consists primarily of costs related to raw materials, freight and delivery, product warranty, and personnel costs (salaries, bonuses, benefits, and stock-based compensation). Personnel costs in cost of revenue include both direct labor costs as well as costs attributable to any individuals whose activities relate to the procurement, installment and delivery of the finished product and services. Deferred cost of revenue results from the timing differences between the costs incurred in advance of the satisfaction of all revenue recognition criteria consistent with our revenue recognition policy. Warranty We provide standard assurance type warranties with our Voyager Trackers for periods generally ranging from five to ten years. We record a provision for estimated warranty expenses, net of amounts recoverable from manufacturers, to cost of sales when we recognize revenue. These estimates are based on our historical experience and forward-looking factors including the expected nature and frequency of product failure rates and costs to address future claims. These estimates are inherently uncertain given our relatively short history of sales and changes to our historical or projected warranty experience may result in material changes to our warranty reserve in the future. We do not maintain general or unspecified reserves; all warranty reserves are related to specific projects. All actual or estimated costs incurred in subsequent periods are charged to those established reserves. Remaining Performance Obligations Remaining performance obligations relate to contracts that have original expected durations of one year or less. Therefore, the transaction price allocated to performance obligations that are unsatisfied or partially satisfied as of the end of the reporting period are not required to be disclosed under ASC 606.	Revenue Recognition Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, (Topic 606), as amended (“ASC 606”) using full retrospective approach. The Company recognizes revenue from the sale of Voyager Single-Axis Solar Tracker (the “Voyager Tracker”), software, and engineering services. Revenue from engineering services is immaterial for the years ended December 31, 2020 and 2019. The Company recognizes revenue when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services by following a five-step process, (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when or as the Company satisfies a performance obligation, as further described below. Identify the contract with a customer: A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the products and services to be transferred and identifies the payment terms related to these products and services, (ii) the contract has commercial substance and, (iii) the Company determines that collection of substantially all consideration for products and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. In assessing the recognition of revenue, the Company also evaluates whether two or more contracts should be combined and accounted for as one contract and if the combined or single contract should be accounted for as multiple performance obligations which could change the amount of revenue and profit (loss) recorded in a period. Change orders may include changes in specifications or design, manner of performance, equipment, materials, scope of work, and/or the period of completion of the project. The Company analyzes its change orders to determine if they should be accounted for as a modification to an existing contract or a new stand-alone contract. The Company’s change orders are generally modifications to existing contracts and are included in the total estimated contract revenue when it is probable that the change order will result in additional value that can be reliably estimated and realized. Identify the performance obligations in the contract: The Company enters into contracts that can include various combinations of products and services, which are either capable of being distinct and accounted for as separate performance obligations or as one performance obligation, as the majority of tasks and services is part of a single project or capability. However, determining whether products or services are considered distinct performance obligations that should be accounted for separately versus together may sometimes require significant judgment. Performance obligations include the sale of Voyager Tracker, customized components of Voyager Tracker, sale of individual parts of Voyager Tracker for certain specific transactions, shipping and handling services, sale of term-based software licenses, maintenance, and support services in connection with the term-based software licenses and sale of software as a service subscription (“Subscription services”) Determine the transaction price: The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring services to the customer. Such amounts are typically stated in the customer contract and to the extent that the Company identifies variable consideration, the Company estimates the variable consideration at the onset of the arrangement as long as it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. None of the Company’s contracts contain a significant financing component. Taxes collected from customers and remitted to governmental authorities are not included in revenue. The majority of the Company’s contracts do not contain variable consideration provisions as a continuation of the original contract. Allocate the transaction price to performance obligations in the contract: Once the Company has determined the transaction price, the total transaction price is allocated to each performance obligation in a manner depicting the amount of consideration to which the Company expects to be entitled in exchange for transferring the good(s) or service(s) to the customer. The Company allocates the transaction price to each performance obligation identified in the contract on a relative standalone selling price basis. The Company uses the expected cost-plus margin approach based on hardware, labor, and related overhead cost to estimate the standalone selling price of the Voyager Tracker, customized components of Voyager Tracker, and individual parts of Voyager Tracker for certain specific transactions. The Company uses the adjusted market assessment approach for all other performance obligations except shipping, handling, and logistics. For shipping, handling, and logistics performance obligation, the Company uses residual approach to calculate the standalone selling price, because of the nature of highly variable and broad range of prices it charges to various customers for this performance obligation in the contracts. Recognize revenue when or as the Company satisfies a performance obligation: For each performance obligation identified, we determine at contract inception whether we satisfy the performance obligation over time or at a point in time. The Company’s performance obligations for the customer specific Voyager Tracker and customized components of Voyager Tracker are satisfied over-time as the work progresses because the Company’s performance does not create an asset with an alternative use to the Company, due to the highly customized nature of the product, and the Company has an enforceable right to payment for performance completed to date. The Company’s performance obligation for shipping and handling services is satisfied over-time as the services are delivered over the term of the contract. The Company’s subscription services sales/ other services are recognized on a straight-line basis over the contract period. The Company’s performance obligations for individual part sales for certain specific transactions are recognized point-in-time as and when control transfers based on the Incoterms for the contract. The Company’s performance obligations for term-based software licenses are recognized point-in-time as and when control transfers based on delivery of license.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Standards In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 removes certain exceptions related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of the guidance to help simplify and promote consistent application of GAAP. The Company adopted ASU 2019-12 in the first quarter of 2021, and the adoption had no material impact to the Company’s consolidated financial statements. New Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 changes the impairment model for most financial assets and requires the use of an expected loss model in place of the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The Company is currently evaluating the impact that the adoption of ASU 2016-13 will have on its condensed consolidated financial statements and the Company plans to adopt effective January 1, 2023. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting. This standard provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. Entities may apply this ASU upon issuance through December 31, 2022 on a prospective basis. The Company is currently evaluating the impact this adoption will have on the Company’s condensed consolidated financial statements and will apply this guidance to transactions and modifications of these arrangements as appropriate.	Recent Accounting Pronouncements Recently Adopted Accounting Standards In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The Company adopted the new standard effective January 1, 2020. The impact of adoption was not material to the Company’s Consolidated Financial Statements. New Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 removes certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of the guidance to help simplify and promote consistent application of GAAP. The guidance is effective for the Company for its fiscal year beginning after December 15, 2021, to the extent the Company remains an emerging growth company, and early adoption is permitted. The Company is currently assessing the impact that the adoption of ASU 2019-12 will have on its consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 changes the impairment model for most financial assets and requires the use of an expected loss model in place of the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The update to the standard is effective for the Company for its fiscal year beginning after December 15, 2022, to the extent the Company remains an emerging growth company, and early adoption is permitted. The Company does not expect the adoption of ASU 2016-13 to have a material impact on its consolidated financial statements.

Accrued Expenses and Other Current Liabilities (FY) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accrued Expenses and Other Current Liabilities Abstract

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	December 31, 2020	September 30, 2021
Accrued cost of revenue	$ 7,812	$33,279
Accrued expenses	2,856	3,205
Warranty reserves	3,985	1,183
Accrued compensation	2,869	1,766
Accrued interest expense	28	128
Other	945	685
Total	$18,495	$40,246

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2019	2020
Accrued cost of revenue	$2,106	$ 7,812
Accrued expenses	1,644	2,856
Warranty reserves	1,368	3,985
Accrued compensation	177	2,869
Accrued interest expense	47	28
Other	33	945
Total	$5,375	$18,495

Prepaid Expenses and Other Current Assets (FY) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Prepaid Expense and Other Assets, Current [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31, 2020	September 30, 2021
Vendor deposits	$4,205	$18,125
Prepaid expenses	1,043	4,060
Deferred cost of revenue	992	—
Surety collateral	113	246
Other current assets	571	1,127
	$6,924	$23,558

Prepaid expenses and other current assets consist of the following (in thousands):

	As of December 31,
	2019	2020
Vendor deposits	$1,738	$4,205
Prepaid expenses	209	1,043
Deferred cost of revenue	19	992
Surety collateral^*	1,835	113
Other current assets	47	571
	$3,848	$6,924

*	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Equity Method Investments (FY) (Tables)

12 Months Ended

Dec. 31, 2020

Equity Method Investments and Joint Ventures [Abstract]

Summary of Equity Method Investments

Equity method investments are as follows (in thousands, except percentages):

Summary of Equity Method Investments Financial Information

Summarized financial information for the Company’s equity method investment is as follows:

Balance sheet (in thousands)

	As of December 31,
	2019	2020
Current assets	$4,466	$10,162
Non-current assets	13,123	9,045
Current liabilities	3,219	12,350
Non-current liabilities	14,344	9,723
Members’ equity (deficit)	25	(2,866)

Statement of operations (in thousands)

	Years Ended December 31
	2019	2020
Revenue	$—	$22,570
Gross profit	—	17,360
Income (loss) from operations	(3,413)	9,185
Net income (loss)	(2,987)	5,933
Share of earnings from equity method investment	(709)	1,399

Intangible Assets, Net (FY) (Tables)

12 Months Ended

Dec. 31, 2020

Intangible Assets, Net [Abstract]

Acquired Intangible Assets

Acquired intangible assets, comprising of developed technology in the form of software tools, subject to amortization were as follows (in thousands):

		As of December 31,
	Estimated Useful Lives (Years)	2019	2020
Developed technology	3	1,200	1,200
Total intangible assets		1,200	1,200
Less: accumulated amortization		1,167	1,200
Total intangible assets, net		$ 33	$ —

Commitments and Contingencies (FY) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Summary of Changes in Product Warranty Reserves

Changes in the Company’s product warranty reserves were as follows (in thousands):

			September 30, 2021
Balance at beginning of period, December 31, 2020			$ 6,811
Warranties issued during the period			2,902
Settlements made during the period			(3,507)
Changes in liability for pre-existing warranties			(783)
Balance at end of period			$ 5,423

Changes in the Company’s product warranty reserves were as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance at beginning of period	$ —	$ 2,057
Warranties issued during the period	2,057	7,866
Settlements made during the period	—	(3,111)
Changes in liability for pre-existing warranties	—	(1)
Balance at end of period	$2,057	$ 6,811

Leases (FY) (Tables)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Supplemental Balance Sheet Information of Leases

Supplemental balance sheet information related to leases was as follows (in thousands):

	As of December 31,
Reported as:	2019	2020
Assets:
Operating lease right of use assets (included in Other assets)	$43	$571
Liabilities:
Operating lease liabilities, current portion (included in Accrued expenses and other current liabilities)	$11	$242
Operating lease liabilities, non-current (included in Other non-current liabilities)	27	355
Total operating lease liabilities	$38	$597

Supplemental Information, Operating Lease

Supplemental information related to operating leases was as follows (in thousands):

	As of December 31,
	2019	2020
Cash payments for operating leases	$38	$140
New operating lease assets obtained in exchange for operating lease liabilities	$42	$672

Future Minimum Lease Payments under Non-cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 are as follows (in thousands):

2021			$266
2022			241
2023			128
Total future lease payments			$635
Less imputed interest			(38)
Total lease liability			$597

Stock Plans (FY) (Tables)

12 Months Ended

Dec. 31, 2020

Stock Plans [Abstract]

Stock Option Activity

The following table summarizes stock option activity under the Plan and related information:

	Options Outstanding
	Number of Shares	Weighted Average Exercise Price	Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding - December 31, 2019	8,081,739	$0.22
Granted during the year	525,725	0.48
Exercised or released	—	—
Cancelled or forfeited	82,467	0.07
Expired	—	—
Balances - December 31, 2020	8,524,997	$0.23	7.51	$25,785
Vested and expected to vest - December 31, 2020	8,524,997	$0.23	7.51	$25,785
Exercisable - December 31, 2020	5,379,164	$0.16	7.11	$16,693

Restricted Stock Activity

The following summarizes restricted stock activity under the Plan:

	Unvested Restricted Stock Units		Unvested Restricted Stock Awards
	Number of Shares	Weighted- Average Intrinsic Value	Number of Shares	Weighted- Average Grant Date Fair Value
Unvested as of December 31, 2019	824,667	$1.64	4,424,652	$0.07
Granted	12,201,611	3.26	—	—
Vested	—	—	3,255,052	0.07
Forfeited or canceled	82,467	3.26	—	—
Unvested as of December 31, 2020	12,943,811	$ 3.16	1,169,600	$0.07

Components of Stock-Based Compensation Expense

The Company recognized stock-based compensation expense under the Plan (in thousands):

	Years Ended December 31,
	2019	2020
Cost of revenue	$176	322
General and administrative	653	1,401
Research and development	51	57
Selling and marketing	26	38
Total stock-based compensation expense	$906	1,818

Assumptions Used in Determining Fair Value of Options

The fair value of stock options granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:

	Years Ended December 31,
	2019	2020
Expected term (years)	5.66–6.09	5.99–6.17
Expected volatility	52.01%—54.10%	51.52%—51.58%
Risk-free interest rate	1.63%—2.3%	1.60%—1.61%
Expected dividends	—	—
Grant date fair value per option	$1.27—$1.30	$2.85—$2.86

Net Loss Per Share (FY) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Net Loss Per Share [Abstract]

Schedule of Computation of Basic and Diluted Income (Loss) Per Share

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
Basic and diluted:
Net loss	$ (2,840)	$ (22,916)	$ (6,196)	$ (82,707)
Basic weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Diluted weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Basic loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)
Diluted loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)

The table below sets forth the computation of basic and diluted loss per share (in thousands, except per share amounts):

	Years Ended December 31,
	2019	2020
Basic and diluted:
Net loss	$(13,495)	$(15,924)
Weighted-average number of common shares outstanding	62,043	68,811
Basic and diluted loss per share	$(0.22)	$(0.23)

Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Income Per Share

The following potentially dilutive securities were excluded (in thousands):

	As of September 30,
	2020	2021
Shares of common stock issuable under stock option plans outstanding	8,566	9,610
Shares of common stock issuable upon vesting of restricted stock awards	13,622	5,598
Potential common shares excluded from diluted net loss per share	22,188	15,208

The following potentially dilutive securities were excluded (in thousands):

	As of December 31,
	2019	2020
Shares of common stock issuable under stock option plans outstanding	8,082	8,525
Shares of common stock issuable upon vesting of restricted stock awards	5,249	14,122
Potential common shares excluded from diluted net loss per share	13,331	22,647

Income Taxes (FY) (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

U.S. and Foreign Income (Loss) Before Income Taxes

The following table summarizes our U.S. and foreign income (loss) before income taxes (in thousands):

	Years Ended December 31,
	2019	2020
U.S.	$(13,534)	$(16,269)
Foreign	—	262
Total loss before income taxes	$(13,534)	$(16,007)

Provision for Income Tax Expense (Benefit)

	Years Ended December 31,
	2019	2020
Current
Federal	$—	$(159)
State	(37)	1
Foreign	—	78
Deferred
Federal	(2)	(3)
State	—	—
Total income tax expense/(benefit)	$(39)	$(83)

Income Tax Rate Reconciliation

	Years Ended December 31,
	2019	2020
Income tax expense (benefit) derived by applying the federal statutory tax rate to income (loss) before income taxes	$(2,842)	$(3,362)
State taxes, net of federal	(551)	(215)
Research and experimentation tax credit	(118)	(179)
Valuation allowance	3,184	3,523
Stock compensation	225	406
Dividends received deduction	—	(308)
Permanent differences and other	63	52
	$(39)	$(83)

Deferred Income Tax Assets and Liabilities

The Company’s deferred income tax assets and liabilities were comprised of the following (in thousands):

	As of December 31,
	2019	2020
Deferred tax assets:
Fixed assets and intangibles	$156	$135
Leases	—	106
Accrued expenses	333	2,066
Net operating loss carryforward	4,626	6,679
Capital loss carryforward	501	—
Investment difference	—	148
R&D credit carryforward	181	325
Subtotal	5,797	9,459
Less valuation allowance	(5,774)	(9,297)
Total deferred tax asset	23	162
Deferred tax (liabilities):
Investment difference	(15)	—
Leases	—	(101)
Prepaid expenses	(11)	(61)
Total deferred tax (liability)	(26)	(162)
Net deferred tax asset (liability)	$(3)	$—

Reconciliation of Unrecognized Tax Benefits

We account for uncertainty in taxes in accordance with authoritative guidance. A reconciliation of the unrecognized tax benefits is as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance, beginning of the year	$22	$45
Increase for tax positions related to the current year	23	36
Decrease for tax positions related to prior years	—	—
Balance, end of year	$45	$81

Segment Information (FY) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Segment Reporting [Abstract]

Schedule of Company's Total Revenue by Geographic Area

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
United States	$59,591	$52,984	$143,034	$168,540
Other	49	5	139	264
Total net revenue	$59,640	$52,989	$143,173	$168,804

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Years Ended December 31,
	2019	2020
United States	$45,264	$187,093
Vietnam	7,149	38
Other	711	221
Total net revenue	$53,124	$187,352

Revision of Previously Issued Financial Statements (Q3) (Tables)

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Revision of Previously Issued Financial Statements

The errors had no impact on total cash flows for operating, investing, or financing activities, but did impact line items in the indirect method of operating cash flow presentation as shown below:

	As of and for Three Months Ended June 30, 2021 (As Previously Reported)	Adjustments	As of and for Three Months Ended June 30, 2021 (As Revised)
	(in thousands, except share and per share data)
Condensed Consolidated Balance Sheet
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue - Product	$43,885	$(7)	$43,878
Research and development	5,585	(2)	5,583
Selling and Marketing	3,258	(161)	3,097
General and administrative	51,063	(3,321)	47,742
Total operating expenses	59,906	(3,484)	56,422
Loss from operations	(75,963)	3,491	(72,472)
Loss before income taxes	(55,590)	3,491	(52,099)
Net loss	(55,841)	3,491	(52,350)
Comprehensive loss	(55,834)	3,491	(52,343)
Net loss per share - basic	(0.70)	0.09	(0.61)
Net loss per share - diluted	(0.70)	0.09	(0.61)
Weighted-average common shares outstanding-basic	79,229,174	6,927,135	86,156,309
Weighted-average common shares outstanding - diluted	79,229,174	6,927,135	86,156,309
Condensed Consolidated Statement of Stockholders’ Equity
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Net loss	(55,841)	3,491	(52,350)
Stock-based compensation	56,192	(3,491)	52,701
Note 11. Net loss per share
Net loss	$(55,841)	$3,491	$(52,350)
Basic weighted-average number of common shares outstanding	79,229,174	6,927,135	86,156,309
Diluted weighted-average number of common shares outstanding	79,229,174	6,927,135	86,156,309
Basic loss per share	(0.70)	0.09	(0.61)
Diluted loss per share	(0.70)	0.09	(0.61)

	As of and for Six Months Ended June 30, 2021 (As Previously Reported)	Adjustments	As of and for Six Months Ended June 30, 2021 (As Revised)
	(in thousands, except share and per share data)
Condensed Consolidated Balance Sheet
Additional paid-in capital	$286,687	$(3,491)	$283,196
Accumulated deficit	(105,926)	3,491	(102,435)
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue - Product	$98,881	$(7)	$98,874
Research and development	7,539	(2)	7,537
Selling and Marketing	4,358	(161)	4,197
General and administrative	56,147	(3,321)	52,826
Total operating expenses	68,044	(3,484)	64,560
Loss from operations	(83,982)	3,491	(80,491)
Loss before income taxes	(62,833)	3,491	(59,342)
Net loss	(63,283)	3,491	(59,792)
Comprehensive loss	(63,277)	3,491	(59,786)
Net loss per share - basic	(0.87)	0.09	(0.78)
Net loss per share - diluted	(0.87)	0.09	(0.78)
Weighted-average common shares outstanding - basic	73,106,935	3,474,582	76,581,517
Weighted-average common shares outstanding - diluted	73,106,935	3,474,582	76,581,517
Condensed Consolidated Statement of Cash Flows
Net loss	$ (63,283)	$ 3,491	$ (59,792)
Stock-based compensation	56,641	(3,491)	53,150
Note 11. Net loss per share
Net loss	$ (63,283)	$ 3,491	$ (59,792)
Basic weighted-average number of common shares outstanding	73,106,935	3,474,582	76,581,517
Diluted weighted-average number of common shares outstanding	73,106,935	3,474,582	76,581,517
Basic loss per share	(0.87)	0.09	(0.78)
Diluted loss per share	(0.87)	0.09	(0.78)
Shares of common stock issuable upon vesting of restricted stock awards	15,079	(9,885)	5,194
Potential common shares excluded from diluted net loss per share	23,231	(9,885)	13,346

Prepaid Expenses and Other Current Assets (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Prepaid Expense and Other Assets, Current [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31, 2020	September 30, 2021
Vendor deposits	$4,205	$18,125
Prepaid expenses	1,043	4,060
Deferred cost of revenue	992	—
Surety collateral	113	246
Other current assets	571	1,127
	$6,924	$23,558

Prepaid expenses and other current assets consist of the following (in thousands):

	As of December 31,
	2019	2020
Vendor deposits	$1,738	$4,205
Prepaid expenses	209	1,043
Deferred cost of revenue	19	992
Surety collateral^*	1,835	113
Other current assets	47	571
	$3,848	$6,924

*	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Accrued Expenses and Other Current Liabilities (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accrued Expenses and Other Current Liabilities Abstract

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	December 31, 2020	September 30, 2021
Accrued cost of revenue	$ 7,812	$33,279
Accrued expenses	2,856	3,205
Warranty reserves	3,985	1,183
Accrued compensation	2,869	1,766
Accrued interest expense	28	128
Other	945	685
Total	$18,495	$40,246

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2019	2020
Accrued cost of revenue	$2,106	$ 7,812
Accrued expenses	1,644	2,856
Warranty reserves	1,368	3,985
Accrued compensation	177	2,869
Accrued interest expense	47	28
Other	33	945
Total	$5,375	$18,495

Commitments and Contingencies (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Summary of Changes in Product Warranty Reserves

Changes in the Company’s product warranty reserves were as follows (in thousands):

			September 30, 2021
Balance at beginning of period, December 31, 2020			$ 6,811
Warranties issued during the period			2,902
Settlements made during the period			(3,507)
Changes in liability for pre-existing warranties			(783)
Balance at end of period			$ 5,423

Changes in the Company’s product warranty reserves were as follows (in thousands):

	Years Ended December 31,
	2019	2020
Balance at beginning of period	$ —	$ 2,057
Warranties issued during the period	2,057	7,866
Settlements made during the period	—	(3,111)
Changes in liability for pre-existing warranties	—	(1)
Balance at end of period	$2,057	$ 6,811

Net Loss Per Share (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Net Loss Per Share [Abstract]

Schedule of Computation of Basic and Diluted Income (Loss) Per Share

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
Basic and diluted:
Net loss	$ (2,840)	$ (22,916)	$ (6,196)	$ (82,707)
Basic weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Diluted weighted-average number of common shares outstanding	67,567,724	94,596,519	69,857,468	82,677,824
Basic loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)
Diluted loss per share	$ (0.04)	$ (0.24)	$ (0.09)	$ (1.00)

The table below sets forth the computation of basic and diluted loss per share (in thousands, except per share amounts):

	Years Ended December 31,
	2019	2020
Basic and diluted:
Net loss	$(13,495)	$(15,924)
Weighted-average number of common shares outstanding	62,043	68,811
Basic and diluted loss per share	$(0.22)	$(0.23)

Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Income Per Share

The following potentially dilutive securities were excluded (in thousands):

	As of September 30,
	2020	2021
Shares of common stock issuable under stock option plans outstanding	8,566	9,610
Shares of common stock issuable upon vesting of restricted stock awards	13,622	5,598
Potential common shares excluded from diluted net loss per share	22,188	15,208

The following potentially dilutive securities were excluded (in thousands):

	As of December 31,
	2019	2020
Shares of common stock issuable under stock option plans outstanding	8,082	8,525
Shares of common stock issuable upon vesting of restricted stock awards	5,249	14,122
Potential common shares excluded from diluted net loss per share	13,331	22,647

Segment Information (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Segment Reporting [Abstract]

Schedule of Company's Total Revenue by Geographic Area

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Three Months Ended September 30,		Nine Months Ended September 30,
	2020	2021	2020	2021
United States	$59,591	$52,984	$143,034	$168,540
Other	49	5	139	264
Total net revenue	$59,640	$52,989	$143,173	$168,804

The following table summarizes the Company’s total revenue by geographic area based on the billing address of the customers (in thousands):

	Years Ended December 31,
	2019	2020
United States	$45,264	$187,093
Vietnam	7,149	38
Other	711	221
Total net revenue	$53,124	$187,352

Description of Business - Additional Information (FY) (Details) $ in Millions	Jan. 13, 2017 USD ($)
SunEdison Utility Holdings, Inc. [Member]
Description Of Business [Line Items]
Total transaction price	$ 6

Summary of Significant Accounting Policies - Additional Information (FY) (Details)		3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 28, 2021 $ / shares shares	Mar. 31, 2021	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) Customer $ / shares shares	Dec. 31, 2019 USD ($) Customer $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 $ / shares shares
Stock split	8.25-for-1
Forward stock split			8.25	8.25
Common stock, par value \| $ / shares	$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001
Common stock, shares authorized \| shares			850,000,000	98,960,064	98,960,064		98,960,064
Preferred stock, shares authorized \| shares			10,000,000	10,000,000
Preferred stock, par value \| $ / shares			$ 0.0001	$ 0.0001
Cash			$ 140,662,000	$ 32,359,000	$ 7,221,000
Restricted cash				1,000,000.0	1,000,000.0
Financial instruments measured at fair value on a recurring basis				0	0
Raw material				0.0	200,000
Finished goods				$ 1,700,000	4,300,000
Estimated useful life				3 years
Amortization expense				$ 0	0
Long lived assets impaired				0	0
Contract assets				0	0
Deferred revenue				23,000,000.0	19,900,000	$ 200,000
Deferred revenue recognized				$ 19,900,000	$ 200,000
Deferred revenue recognized percentage				100.00%	100.00%
Advertising costs				$ 100,000	$ 300,000
Allowance for doubtful accounts					0
Deferred offering costs					$ 0
Other Assets [Member]
Deferred offering costs				$ 1,600,000
Software [Member]
Estimated useful life				3 years
Revenues [Member]
Number of customers \| Customer				4	3
Accounts Receivable [Member]
Number of customers \| Customer				3	3
Geographic Concentration Risk [Member] \| Revenues [Member] \| Customer One [Member]
Concentration of credit risk				21.00%	59.00%
Geographic Concentration Risk [Member] \| Revenues [Member] \| Customer Two [Member]
Concentration of credit risk				19.00%	21.00%
Geographic Concentration Risk [Member] \| Revenues [Member] \| Customer Three [Member]
Concentration of credit risk				10.00%	13.00%
Geographic Concentration Risk [Member] \| Revenues [Member] \| Customer Four [Member]
Concentration of credit risk				10.00%
Geographic Concentration Risk [Member] \| Accounts Receivable [Member] \| Customer One [Member]
Concentration of credit risk				32.00%	49.00%
Geographic Concentration Risk [Member] \| Accounts Receivable [Member] \| Customer Two [Member]
Concentration of credit risk				25.00%	23.00%
Geographic Concentration Risk [Member] \| Accounts Receivable [Member] \| Customer Three [Member]
Concentration of credit risk				14.00%	18.00%
Minimum [Member]
Estimated useful life of property and equipment				2 years
Subscription revenue contract terms		1 year		1 year
Product warranty life			5 years	5 years
Maximum [Member]
Estimated useful life of property and equipment				5 years
Subscription revenue contract terms		2 years		2 years
Product warranty life			10 years	10 years
Subsequent Event [Member]
Stock split	8.25-for-1
Common stock, par value \| $ / shares	$ 0.0001
Authorized shares of all classes of stock \| shares	860,000,000
Common stock, shares authorized \| shares	850,000,000
Preferred stock, shares authorized \| shares	10,000,000
Preferred stock, par value \| $ / shares	$ 0.0001

Revenue - Additional Information (FY) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue allocated to remaining performance obligations, amount of revenue expected to be recognized		$ 23.0	$ 19.9
Revenue allocated to remaining performance obligations, percentage of revenue expected to be recognized		100.00%
Revenue allocated to remaining performance obligations, expected timing of satisfaction		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue allocated to remaining performance obligations, amount of revenue expected to be recognized		$ 23.0	$ 19.9
Revenue allocated to remaining performance obligations, percentage of revenue expected to be recognized	100.00%
Revenue allocated to remaining performance obligations, expected timing of satisfaction	12 months

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (FY) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities Abstract
Accrued cost of revenue	$ 33,279	$ 7,812	$ 2,106
Accrued expenses	3,205	2,856	1,644
Warranty reserves	1,183	3,985	1,368
Accrued compensation	1,766	2,869	177
Accrued interest expense	128	28	47
Other	685	945	33
Total	$ 40,246	$ 18,495	$ 5,375

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (FY) (Details) - USD ($)
$ in Thousands

Sep. 30, 2021

Dec. 31, 2020

Dec. 31, 2019

Prepaid Expense and Other Assets, Current [Abstract]

Vendor deposits

$ 18,125

$ 4,205

$ 1,738

Prepaid expense

4,060

1,043

209

Deferred cost of revenue

992

Surety collateral

246

113

^[1]

1,835

^[1]

Other current assets

1,127

571

Prepaid expenses and other current assets, Total

$ 23,558

$ 6,924

$ 3,848

[1]	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Equity Method Investments - Summary of Equity Method Investments (FY) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Carrying value	$ 0	$ 1,857	$ 2,582
Dimension Energy [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value		$ 1,857	$ 2,582
Ownership percentage		23.60%	23.70%

Equity Method Investments - Additional Information (FY) (Details) - Dimension Energy [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jun. 24, 2021
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	23.60%	23.70%
Net income (loss)	$ 1.4	$ 0.7
Cash distribution received	$ 2.1
Common Class A [Member]
Schedule Of Equity Method Investments [Line Items]
Number of shares owned	4,791,566	4,791,566
Ownership percentage	24.00%	24.00%	23.00%

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22663-107794

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124452729-227067

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3000-108585

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569616-111683

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 23: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669625-108580

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 29: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 31: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4J
-URI http://asc.fasb.org/extlink&oid=120409616&loc=SL4591551-111686

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4K
-URI http://asc.fasb.org/extlink&oid=120409616&loc=SL4591552-111686

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22658-107794

+ Details

Equity Method Investments - Summarized Financial Information For Equity Method Investments (FY) (Details) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Balance sheet
Current assets	$ 229,164,000				$ 229,164,000		$ 65,717,000	$ 30,636,000
Current liabilities	66,408,000				66,408,000		59,809,000	33,724,000
Statement of operations
Gross profit	(8,039,000)	$ 2,866,000			(23,970,000)	$ 8,464,000	3,639,000	(1,951,000)
Net Income (loss)	(22,916,000)	(2,840,000)	$ (59,792,000)	$ (3,356,000)	(82,707,000)	(6,196,000)	(15,924,000)	(13,495,000)
Share of earnings from equity method investment	$ (400)	$ (186,000)			$ (354,000)	$ (345,000)	1,399,000	(709,000)
Dimension Energy [Member]
Balance sheet
Current assets							10,162,000	4,466,000
Non-current assets							9,045,000	13,123,000
Current liabilities							12,350,000	3,219,000
Non-current liabilities							9,723,000	14,344,000
Members' equity (deficit)							(2,866,000)	25,000
Statement of operations
Total revenue							22,570,000	0
Gross profit							17,360,000	0
Income (loss) from operations							9,185,000	(3,413,000)
Net Income (loss)							5,933,000	(2,987,000)
Share of earnings from equity method investment							$ 1,399,000	$ (709,000)

Intangible Assets, Net (FY) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Finite-Lived Intangible Assets, Net [Abstract]
Total intangible assets	$ 1,200		$ 1,200
Less: accumulated amortization	1,200		1,167
Total intangible assets, net	$ 0	$ 33	$ 33
Estimated Useful Lives (Years)	3 years
Amortization expense related to intangible assets	$ 0	$ 400
Estimated amortization expense	$ 0

Debt and Other Borrowings - Additional Information (FY) (Details) - USD ($)					3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 20, 2021	Apr. 30, 2020	Jun. 17, 2019	Jan. 30, 2017	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Debt Instrument [Line Items]
Common stock issued for notes purchased					84,944,145		84,944,145		66,155,340	63,633,981	9,162,976
Gain (loss) on extinguishment of debt					$ 0	$ (34,000)	$ 790,000	$ (75,000)	$ (116,000)	$ 0
Interest expense on debt and other borrowings					$ 300,000	$ 100,000	$ 500,000	$ 300,000	500,000	500,000
Revolving Line of Credit
Debt Instrument [Line Items]
Term of notes							3 years
Revolving Line of Credit \| Western Alliance Bank [Member]
Debt Instrument [Line Items]
Principal amount			$ 1,000,000.0
Maturity period			2 years
Initial margins			5.50%
Line of credit, outstanding balance									$ 1,000,000.0	$ 1,000,000.0
The Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount of notes				$ 7,000,000
Term of notes				5 years
Common stock issued for notes purchased				25,000
Promissory notes purchased				$ 250,000
Interest rate of notes				5.00%
The Notes [Member] \| Private Placement [Member]
Debt Instrument [Line Items]
Aggregate principal amount of notes				$ 7,000,000.0
Term of notes				5 years
Common stock issued for notes purchased				25,000
Promissory notes purchased				$ 250,000
Interest rate of notes				5.00%
Paycheck Protection Program ('PPP') Loan [Member] \| CARES Act [Member]
Debt Instrument [Line Items]
Maturity period		2 years
Initial margins		1.00%
Loans received		$ 800,000
Gain (loss) on extinguishment of debt	$ 800,000
Paycheck Protection Program ('PPP') Loan [Member] \| CARES Act [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt	$ 800,000

Commitments and Contingencies - Additional Information (FY) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities [Member]
Product Warranty Liability [Line Items]
Warranty reserves	$ 1.2	$ 4.0	$ 1.4
Other Noncurrent Liabilities [Member]
Product Warranty Liability [Line Items]
Warranty reserves	$ 4.2	$ 2.8	$ 0.7

Commitments and Contingencies - Summary of Changes in Product Warranty Reserves (FY) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Balance at beginning of period	$ 6,811	$ 2,057	$ 0
Warranties issued during the period	2,902	7,866	2,057
Settlements made during the period	(3,507)	(3,111)	0
Changes in liability for pre-existing warranties	(783)	(1)	0
Balance at end of period	$ 5,423	$ 6,811	$ 2,057

Leases, Additional Information (FY) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Operating Lease, Description [Abstract]
Operating lease expense	$ 0.2	$ 0.1
Minimum [Member]
Lessee, Operating Lease, Description [Abstract]
Operating lease term	12 months
Maximum [Member]
Lessee, Operating Lease, Description [Abstract]
Operating lease term	39 months

Leases, Supplemental Balance Sheet Information of Leases (FY) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Operating lease right of use assets (included in Other assets)	$ 571	$ 43
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets
Liabilities:
Operating lease liabilities, current portion (included in Accrued expenses and other current liabilities)	$ 242	$ 11
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Operating lease liabilities, non-current (included in Other non-current liabilities)	$ 355	$ 27
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities	Other non-current liabilities
Total operating lease liabilities	$ 597	$ 38

Leases, Supplementary Information Operating Lease (FY) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Leases [Abstract]
Cash payments for operating leases	$ 140	$ 38
New operating lease assets obtained in exchange for operating lease liabilities	$ 672	$ 42
Operating lease, weighted average remaining lease term	3 years 29 days	1 year 10 months 17 days
Operating lease, weighted average discount rate, percent	5.00%	5.00%

Leases, Future Minimum Lease Payments under Non-cancelable Operating Leases (FY) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2021	$ 266
2022	241
2023	128
Total future lease payments	635
Less imputed interest	(38)
Total lease liability	$ 597	$ 38

Common Stock (FY) (Details)					9 Months Ended	12 Months Ended
Common Stock (FY) (Details)	Apr. 05, 2021 USD ($) shares	Jan. 08, 2021 USD ($) shares	Jul. 21, 2020 USD ($) shares	Jul. 21, 2020 USD ($) shares	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) Vote $ / shares shares	Apr. 28, 2021 $ / shares	Dec. 31, 2020 USD ($) $ / shares shares	Mar. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Common Stock [Abstract]
Common stock, shares authorized \| shares					850,000,000	98,960,064		98,960,064		98,960,064
Common stock, par value \| $ / shares					$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001
Dividends \| $					$ 0	$ 0
Number of votes entitled to each share of common stock \| Vote						1
Common stock, shares issued \| shares					84,944,145			66,155,340	9,162,976	63,633,981
Sale of stock, price per share \| $ / shares									$ 3.27
Common stock, value, issued \| $					$ 8,000			$ 1,000	$ 30,000,024	$ 1,000
Treasury stock, shares, acquired \| shares	717,460	148,440	9,896,666	9,896,666
Treasury stock, value \| $	$ 0	$ 0	$ 0	$ 0	$ 0			$ 0		$ 0

Stock Plans, Stock Option Activity (FY) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Shares [Roll Forward]
Outstanding, beginning of period (in shares)	8,081,739
Granted during the year (in shares)	525,725
Exercised or released (in shares)	0
Cancelled or forfeited (in shares)	82,467
Expired (in shares)	0
Balances (in shares)	8,524,997	8,081,739
Vested and expected to vest (in shares)	8,524,997
Exercisable (in shares)	5,379,164
Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 0.22
Granted during the year (in dollars per share)	0.48
Exercised or released (in dollars per share)	0
Cancelled or forfeited (in dollars per share)	0.07
Expired (in dollars per share)	0
Balances (in dollars per share)	0.23	$ 0.22
Vested and expected to vest (in dollars per share)	0.23
Exercisable (in dollars per share)	$ 0.16
Weighted Average Remaining Contractual Term [Abstract]
Weighted average remaining contractual term, Balances	7 years 6 months 3 days
Weighted-average remaining contractual term, Vested and expected to vest	7 years 6 months 3 days
Weighted average remaining contractual term, Exercisable	7 years 1 month 9 days
Aggregate Intrinsic Value [Abstract]
Balances, Aggregate intrinsic value	$ 25,785
Vested and expected to vest, Aggregate intrinsic value	25,785
Exercisable, Aggregate intrinsic value	$ 16,693
Additional Information Related to Stock Options [Abstract]
Stock options vesting period	4 years
Options expiration period	10 years
Weighted-average grant date fair value of options granted (in dollars per share)	$ 1.29	$ 2.86
Aggregate intrinsic value of options exercised	$ 0	$ 0
2017 Stock Incentive Plan [Member]
Share-based Compensation [Abstract]
Shares authorized for grant (in shares)	24,534,509

Stock Plans, Restricted Stock Activity (FY) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Compensation Expense [Abstract]
Vesting period				4 years
Stock-based compensation	$ 5,400	$ 58,531	$ 1,381	$ 1,818	$ 906
Number of Shares [Roll Forward]
Granted (in shares)				9,900,000
Restricted Stock Awards [Member]
Compensation Expense [Abstract]
Vesting period				4 years
Stock-based compensation				$ 200	200
Total unamortized compensation cost				$ 200	$ 100
Number of Shares [Roll Forward]
Unvested beginning balance (in shares)		1,169,600	4,424,652	4,424,652
Granted (in shares)				0
Vested (in shares)				3,255,052
Forfeited or canceled (in shares)				0
Unvested ending balance (in shares)				1,169,600	4,424,652
Weighted-Average Grant Date Fair Value [Abstract]
Unvested beginning balance		$ 0.07	$ 0.07	$ 0.07
Granted (in dollars per share)				0
Vested (in dollars per share)				0.07
Forfeited or canceled (in dollars per share)				0
Unvested ending balance				$ 0.07	$ 0.07
Restricted Stock Units [Member]
Compensation Expense [Abstract]
Vesting period				4 years
Stock issued (in shares)				9,900,000
Stock-based compensation				$ 0
Total unamortized compensation cost				$ 40,800
Number of Shares [Roll Forward]
Unvested beginning balance (in shares)		12,943,811	824,667	824,667
Granted (in shares)				12,201,611
Vested (in shares)				0	0
Forfeited or canceled (in shares)				82,467
Unvested ending balance (in shares)				12,943,811	824,667
Weighted-Average Intrinsic Value [Abstract]
Unvested beginning balance (in dollars per share)		$ 3.16	$ 1.64	$ 1.64
Granted (in dollars per share)				3.26
Vested (in dollars per share)				0
Forfeited or canceled (in dollars per share)				3.26
Unvested ending balance (in dollars per share)				$ 3.16	$ 1.64

Stock Plans, Components of Stock-Based Compensation Expense (FY) (Details) - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock-based Compensation Expense [Abstract]
Total stock-based compensation expense	$ 1,818	$ 906
Unrecognized compensation expense	$ 44,500
Weighted average period recognized	3 years 14 days
Shares granted (in shares)	9.9
Cost of Revenue [Member]
Stock-based Compensation Expense [Abstract]
Total stock-based compensation expense	$ 322	176
General and Administrative [Member]
Stock-based Compensation Expense [Abstract]
Total stock-based compensation expense	1,401	653
Research and Development [Member]
Stock-based Compensation Expense [Abstract]
Total stock-based compensation expense	57	51
Selling and Marketing [Member]
Stock-based Compensation Expense [Abstract]
Total stock-based compensation expense	$ 38	$ 26

Stock Plans, Assumptions Used in Determining Fair Value of Stock Options (FY) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Assumptions for Stock Awards Granted [Abstract]
Expected dividends	$ 0	$ 0
Minimum [Member]
Assumptions for Stock Awards Granted [Abstract]
Expected term	5 years 11 months 26 days	5 years 7 months 28 days
Expected volatility	51.52%	52.01%
Risk-free interest rate	1.60%	1.63%
Grant date fair value per option (in dollars per share)	$ 2.85	$ 1.27
Maximum [Member]
Assumptions for Stock Awards Granted [Abstract]
Expected term	6 years 2 months 1 day	6 years 1 month 2 days
Expected volatility	51.58%	54.10%
Risk-free interest rate	1.61%	2.30%
Grant date fair value per option (in dollars per share)	$ 2.86	$ 1.30

Net Loss Per Share - Schedule of Computation of Basic and Diluted Loss Per Share (FY) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Basic and diluted:
Net loss	$ (22,916)	$ (2,840)	$ (59,792)	$ (3,356)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Basic weighted-average number of common shares outstanding	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Diluted weighted-average number of common shares outstanding	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Basic loss per share	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Diluted loss per share	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1448-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1337-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=125512782&loc=d3e4984-109258

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=125512782&loc=d3e3842-109258

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22644-107794

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1252-109256

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=125512782&loc=d3e4984-109258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22644-107794

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=125512782&loc=d3e3842-109258

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1252-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1337-109256

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Income Per Share (FY) (Details) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	15,208	22,188	22,647,000	13,331,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	9,610	8,566	8,525,000	8,082,000
Restricted Stock Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	5,598	13,622	14,122,000	5,249,000

Income Taxes, U.S. and Foreign Income (Loss) Before Income Taxes (FY) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income (Loss) Before Income Taxes [Abstract]
U.S.	$ (16,269)	$ (13,534)
Foreign	262	0
Total loss before income taxes	$ (16,007)	$ (13,534)

Income Taxes, Provision for Income Tax Expense (Benefit) (FY) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Current [Abstract]
Federal					$ (159)	$ 0
State					1	(37)
Foreign					78	0
Deferred [Abstract]
Federal					(3)	(2)
State					0	0
Total income tax expense/(benefit)	$ 41	$ 24	$ 137	$ (115)	$ (83)	$ (39)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes, Income Tax Rate Reconciliation (FY) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit) derived by applying the federal statutory tax rate to income (loss) before income taxes					$ (3,362)	$ (2,842)
State taxes, net of federal					(215)	(551)
Research and experimentation tax credit					(179)	(118)
Valuation allowance					3,523	3,184
Stock compensation					406	225
Dividends received deduction					(308)	0
Permanent differences and other					52	63
Total income tax expense/(benefit)	$ 41	$ 24	$ 137	$ (115)	$ (83)	$ (39)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes, Deferred Income Tax Assets and Liabilities (FY) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets [Abstract]
Fixed assets and intangibles	$ 135	$ 156
Leases	106	0
Accrued expenses	2,066	333
Net operating loss carryforward	6,679	4,626
Capital loss carryforward	0	501
Investment difference	148	0
R&D credit carryforward	325	181
Subtotal	9,459	5,797
Less valuation allowance	(9,297)	(5,774)
Total deferred tax asset	162	23
Deferred Tax (Liabilities) [Abstract]
Investment difference	0	(15)
Leases	(101)	0
Prepaid expenses	(61)	(11)
Total deferred tax (liability)	(162)	(26)
Net deferred tax asset (liability)	0	(3)
Change in total valuation allowance	3,500	$ 3,100
R&D Credit Carryforwards [Member]
Tax Credit Carryforward [Abstract]
Tax credit carryforward	$ 400
Tax credit carryforward, expiration date	Jan. 01, 2038
Federal [Member]
Operating Loss Carryforwards [Abstract]
Operating loss carryforwards	$ 27,800
State [Member]
Operating Loss Carryforwards [Abstract]
Operating loss carryforwards	$ 17,000
Operating loss carryforwards , expiration date	Jan. 01, 2034

Income Taxes, Reconciliation of Unrecognized Tax Benefits (FY) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021
Changes in unrecognized tax benefits [Roll Forward]
Balance, beginning of the year	$ 45	$ 22
Increase for tax positions related to the current year	36	23
Decrease for tax positions related to prior years	0	0
Balance, end of year	81	45
Income Tax Interest and Penalties Accrued	$ 0	$ 0	$ 0

Retirement Plan (FY) (Details) - USD ($)	12 Months Ended
Retirement Plan (FY) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Retirement Plan [Abstract]
Contributions by employer	$ 310,000	$ 150,000
Pretax employee contributions	$ 19,500

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References + Details

Segment Information - Additional Information (FY) (Details) - Segment	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of operating segment	1	1
Non US [Member] \| Geographic Concentration Risk [Member] \| Total Revenue [Member] \| Maximum [Member]
Concentration Risk, Percentage		10.00%	10.00%

Segment Information - Schedule of Company's Total Revenue by Geographic Area (FY) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Revenues	$ 52,989	$ 59,640	$ 168,804	$ 143,173	$ 187,352	$ 53,124
United States [Member]
Revenues	52,984	59,591	168,540	143,034	187,093	45,264
Vietnam [Member]
Revenues					38	7,149
Other [Member]
Revenues	$ 5	$ 49	$ 264	$ 139	$ 221	$ 711

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Related Parties -Additional Information (FY) (Details) - USD ($)						12 Months Ended
	Apr. 05, 2021	Jan. 08, 2021	Jul. 21, 2020	Jul. 21, 2020	Jan. 30, 2017	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Mar. 31, 2020
Related Party Transaction [Line Items]
Common stock issued for notes purchased						66,155,340	63,633,981	84,944,145	9,162,976
Treasury stock, shares, acquired	717,460	148,440	9,896,666	9,896,666
Treasury stock, value	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0	$ 0
The Notes [Member]
Related Party Transaction [Line Items]
Aggregate principal amount of notes					$ 7,000,000
Interest rate of notes					5.00%
Term of notes					5 years
Interest expense						$ 200,000	$ 300,000
Common stock issued for notes purchased					25,000
Promissory notes purchased					$ 250,000
Two Board Members [Member] \| The Notes [Member]
Related Party Transaction [Line Items]
Aggregate principal amount of notes					$ 6,000,000.0

Subsequent Events (FY) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
Subsequent Events (FY) (Details) - USD ($) $ in Thousands	Jan. 20, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Subsequent Event [Abstract]
Gain (loss) on extinguishment of debt		$ 0	$ (34)	$ 790	$ (75)	$ (116)	$ 0
Paycheck Protection Program ('PPP') Loan [Member] \| CARES Act [Member]
Subsequent Event [Abstract]
Gain (loss) on extinguishment of debt	$ 800
Subsequent Event [Member] \| Paycheck Protection Program ('PPP') Loan [Member] \| CARES Act [Member]
Subsequent Event [Abstract]
Gain (loss) on extinguishment of debt	$ 800

Subsequent Events (Unaudited) (FY) (Details) $ in Millions	Apr. 21, 2021 USD ($)
FCX Solar, LLC [Member] \| Subsequent Event [Member]
Subsequent Events (Unaudited) [Abstract]
Loss contingency, damages sought, value	$ 133

Description of Business - Additional Information (Q3) (Details) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended
	Apr. 30, 2021	Apr. 28, 2021	Sep. 30, 2021	Sep. 30, 2020
Description Of Business [Line Items]
Stock issuance costs			$ 5,942	$ 0
Stock split		8.25-for-1
IPO [Member]
Description Of Business [Line Items]
Issuance of common stock (in shares)	19,840,000		4,455,384
Price per share of common stock	$ 13.00
Proceeds from IPO			$ 241,200
Purchase cost of shares	$ 54,200		$ 54,200
Stock split			8.25-for-1
Subsequent Event [Member]
Description Of Business [Line Items]
Stock split		8.25-for-1

Revision of Previously Issued Financial Statements - Schedule of condensed Consolidated Balance Sheet (Q3) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Consolidated Balance Sheet
Additional paid-in capital	$ 288,696					$ 288,696		$ 50,096	$ 18,273
Accumulated deficit	(125,351)					(125,351)		(42,643)	(26,719)
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue	61,028		$ 56,774			192,774	$ 134,709	183,713	55,075
Research and development	2,116		1,438			9,653	4,047	5,222	3,960
Selling and marketing	2,224		1,041			6,421	2,374	3,545	1,897
General and administrative	10,392		2,912			63,217	7,630	11,798	4,563
Total operating expenses	14,732		5,391			79,291	14,051	20,565	10,420
Loss from operations	(22,771)		(2,525)			(103,261)	(5,587)	(16,926)	(12,371)
Loss before income taxes	(22,875)		(2,630)			(82,216)	(5,966)	(17,406)	(12,825)
Net loss	(22,916)		(2,840)	$ (59,792)	$ (3,356)	(82,707)	(6,196)	(15,924)	(13,495)
Comprehensive loss	$ (22,913)		$ (2,852)			$ (82,698)	$ (6,216)	$ (15,927)	$ (13,495)
Basic loss per share	$ (0.24)		$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Diluted loss per share	$ (0.24)		$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Basic weighted-average number of common shares outstanding	94,596,519		67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Diluted weighted-average number of common shares outstanding	94,596,519		67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Statement of Stockholders' Equity [Abstract]
Net Income (loss)	$ (22,916)		$ (2,840)	(59,792)	(3,356)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Stockholders equity	163,359	$ 180,772	16,720	180,772	19,124	163,359	16,720	7,451	(8,445)	$ (1,856)
Statement of Cash Flows [Abstract]
Net loss	(22,916)		(2,840)	(59,792)	(3,356)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Note 11. Net loss per share
Potential common shares excluded from diluted net loss per share						15,208	22,188	22,647,000	13,331,000
Product
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue	48,090		46,513			$ 146,964	$ 114,883	$ 155,967	$ 44,212
Additional Paid-in Capital
Statement of Stockholders' Equity [Abstract]
Stockholders equity	288,696	283,196	49,654	283,196	49,206	288,696	49,654	50,096	18,273	11,367
Accumulated Deficit
Condensed Consolidated Statement of Comprehensive Loss
Net loss	(22,916)		(2,840)	(59,792)	(3,356)			(15,924)	(13,495)
Statement of Stockholders' Equity [Abstract]
Net Income (loss)	(22,916)		(2,840)	(59,792)	(3,356)			(15,924)	(13,495)
Stockholders equity	(125,351)	(102,435)	(32,915)	(102,435)	(30,075)	$ (125,351)	$ (32,915)	(42,643)	(26,719)	$ (13,224)
Statement of Cash Flows [Abstract]
Net loss	$ (22,916)		$ (2,840)	(59,792)	$ (3,356)			$ (15,924)	$ (13,495)
As Previously Reported
Condensed Consolidated Balance Sheet
Additional paid-in capital		286,687		286,687
Accumulated deficit		(105,926)		(105,926)
Condensed Consolidated Statement of Comprehensive Loss
Research and development		5,585		7,539
Selling and marketing		3,258		4,358
General and administrative		51,063		56,147
Total operating expenses		59,906		68,044
Loss from operations		(75,963)		(83,982)
Loss before income taxes		(55,590)		(62,833)
Net loss		(55,841)		(63,283)
Comprehensive loss		$ (55,834)		$ (63,277)
Basic loss per share		$ (0.70)		$ (0.87)
Diluted loss per share		$ (0.70)		$ (0.87)
Basic weighted-average number of common shares outstanding		79,229,174		73,106,935
Diluted weighted-average number of common shares outstanding		79,229,174		73,106,935
Statement of Stockholders' Equity [Abstract]
Net Income (loss)		$ (55,841)		$ (63,283)
Stock-based compensation		56,192		56,641
Statement of Cash Flows [Abstract]
Net loss		(55,841)		(63,283)
Stock-based compensation		56,192		$ 56,641
Note 11. Net loss per share
Shares of common stock issuable upon vesting of restricted stock awards				15,079
Potential common shares excluded from diluted net loss per share				23,231
As Previously Reported \| Product
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue		43,885		$ 98,881
As Previously Reported \| Additional Paid-in Capital
Condensed Consolidated Balance Sheet
Additional paid-in capital		286,687		286,687
As Previously Reported \| Accumulated Deficit
Condensed Consolidated Balance Sheet
Accumulated deficit		(105,926)		(105,926)
Adjustments
Condensed Consolidated Balance Sheet
Additional paid-in capital		(3,491)		(3,491)
Accumulated deficit		3,491		3,491
Condensed Consolidated Statement of Comprehensive Loss
Research and development		(2)		2
Selling and marketing		(161)		161
General and administrative		(3,321)		3,321
Total operating expenses		(3,484)		(3,484)
Loss from operations		3,491		3,491
Loss before income taxes		3,491		3,491
Net loss		3,491		3,491
Comprehensive loss		$ 3,491		$ 3,491
Basic loss per share		$ 0.09		$ 0.09
Diluted loss per share		$ 0.09		$ 0.09
Basic weighted-average number of common shares outstanding		6,927,135		3,474,582
Diluted weighted-average number of common shares outstanding		6,927,135		3,474,582
Statement of Stockholders' Equity [Abstract]
Net Income (loss)		$ 3,491		$ 3,491
Stock-based compensation		(3,491)		(3,491)
Statement of Cash Flows [Abstract]
Net loss		3,491		3,491
Stock-based compensation		(3,491)		$ (3,491)
Note 11. Net loss per share
Shares of common stock issuable upon vesting of restricted stock awards				9,885
Potential common shares excluded from diluted net loss per share				9,885
Adjustments \| Product
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue		7		$ 7
Adjustments \| Additional Paid-in Capital
Condensed Consolidated Balance Sheet
Additional paid-in capital		(3,491)		(3,491)
Adjustments \| Accumulated Deficit
Condensed Consolidated Balance Sheet
Accumulated deficit		3,491		3,491
As Revised
Condensed Consolidated Balance Sheet
Additional paid-in capital		283,196		283,196
Accumulated deficit		(102,435)		(102,435)
Condensed Consolidated Statement of Comprehensive Loss
Research and development		5,583		7,537
Selling and marketing		3,097		4,197
General and administrative		47,742		52,826
Total operating expenses		56,422		64,560
Loss from operations		(72,472)		(80,491)
Loss before income taxes		(52,099)		(59,342)
Net loss		(52,350)		(59,792)
Comprehensive loss		$ (52,343)		$ (59,786)
Basic loss per share		$ (0.61)		$ (0.78)
Diluted loss per share		$ (0.61)		$ (0.78)
Basic weighted-average number of common shares outstanding		86,156,309		76,581,517
Diluted weighted-average number of common shares outstanding		86,156,309		76,581,517
Statement of Stockholders' Equity [Abstract]
Net Income (loss)		$ (52,350)		$ (59,792)
Stock-based compensation		52,701		53,150
Statement of Cash Flows [Abstract]
Net loss		(52,350)		(59,792)
Stock-based compensation		52,701		$ 53,150
Note 11. Net loss per share
Shares of common stock issuable upon vesting of restricted stock awards				5,194
Potential common shares excluded from diluted net loss per share				13,346
As Revised \| Product
Condensed Consolidated Statement of Comprehensive Loss
Cost of Revenue		43,878		$ 98,874
As Revised \| Additional Paid-in Capital
Condensed Consolidated Balance Sheet
Additional paid-in capital		283,196		283,196
As Revised \| Accumulated Deficit
Condensed Consolidated Balance Sheet
Accumulated deficit		$ (102,435)		$ (102,435)

Summary of Significant Accounting Policies - Additional Information (Q3) (Details)		3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 28, 2021 $ / shares	Mar. 31, 2021	Sep. 30, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares	Mar. 31, 2020 shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2017 $ / shares
Stock split	8.25-for-1
Forward stock split			8.25	8.25
Common stock, par value \| $ / shares	$ 0.0001		$ 0.0001	$ 0.0001		$ 0.0001	$ 0.0001
Common stock, shares issued \| shares			84,944,145	66,155,340	9,162,976	63,633,981
Common stock, shares outstanding \| shares			84,944,145	66,155,340		63,633,981
Warranty description		We provide standard assurance type warranties with our Voyager Trackers for periods generally ranging from five to ten years.
Minimum [Member]
Subscription revenue contract terms		1 year		1 year
Product warranty life			5 years	5 years
Maximum [Member]
Subscription revenue contract terms		2 years		2 years
Product warranty life			10 years	10 years
Subsequent Event [Member]
Stock split	8.25-for-1
Common stock, par value \| $ / shares	$ 0.0001

Revenue - Unbilled Revenue (Q3) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue allocated to remaining performance obligations, amount of revenue expected to be recognized		$ 23.0	$ 19.9
Revenue allocated to remaining performance obligations, percentage of revenue expected to be recognized		100.00%
Revenue allocated to remaining performance obligations, expected timing of satisfaction		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue allocated to remaining performance obligations, amount of revenue expected to be recognized		$ 23.0	$ 19.9
Revenue allocated to remaining performance obligations, percentage of revenue expected to be recognized	100.00%
Revenue allocated to remaining performance obligations, expected timing of satisfaction	12 months

Revenue - Contract Liabilities (Q3) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 9,606	$ 22,980	$ 19,873
Unbilled receivables	$ 15,700	$ 1,200

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Q3) (Details) - USD ($)
$ in Thousands

Sep. 30, 2021

Dec. 31, 2020

Dec. 31, 2019

Prepaid Expense and Other Assets, Current [Abstract]

Vendor deposits

$ 18,125

$ 4,205

$ 1,738

Prepaid expense

4,060

1,043

209

Deferred cost of revenue

992

Surety collateral

246

113

^[1]

1,835

^[1]

Other current assets

1,127

571

Prepaid expenses and other current assets, Total

$ 23,558

$ 6,924

$ 3,848

[1]	Surety collateral represents amounts held in deposit to secure performance bonds, which is expected to be ultimately received back in cash when settled.

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Q3) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities Abstract
Accrued cost of revenue	$ 33,279	$ 7,812	$ 2,106
Accrued expenses	3,205	2,856	1,644
Warranty reserves	1,183	3,985	1,368
Accrued compensation	1,766	2,869	177
Accrued interest expense	128	28	47
Other	685	945	33
Total	$ 40,246	$ 18,495	$ 5,375

Sales of Equity Method Investments - Additional Information (Q3) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jun. 24, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 29, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Equity Method Investments [Line Items]
Success Based Fee						$ 1.9
Gain (Loss) on Disposition of Stock in Subsidiary			$ 0.2	$ 0.4	$ 0.3
Business Combination Contingent Consideration Receivable				$ 14.0
Escrow released payment received		$ 0.2
Dimension [Member]
Schedule Of Equity Method Investments [Line Items]
Business Combination, Contingent Consideration Arrangements, Description				The sales agreement with Dimension includes an earnout provision which provides the potential to receive an additional contingent consideration of up to approximately $14.0 million through December 2024, based on Dimension achieving certain performance milestones. This potential earnout is calculated each quarter starting January 1, 2022. The potential payment is calculated as $200 per the number of kilowatts constituting each Notice To Proceed (NTP) megawatt (MW) achieved during such quarterly earnout period, provided that no earnout amount is payable in respect to the first 100 NTP MW achieved in any earnout year. The sales agreement also includes a projects escrow release which is an additional contingent consideration to receive $7 million based on Dimension’s completion of certain construction projects currently in progress
Dimension Energy LLC
Schedule Of Equity Method Investments [Line Items]
Ownership percentage							23.60%	23.70%
Gain (Loss) on Sale of Equity Investments				$ 20.8
Dimension Energy LLC \| Common Class A
Schedule Of Equity Method Investments [Line Items]
Number of Share Disposed	4,791,566
Ownership percentage	23.00%						24.00%	24.00%
Ownership value	$ 22.0
Success Based Fee	$ 1.9

Sales of Equity Method Investments - Summarized Financial Information For Equity Method Investments (Q3) (Details) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Statement of operations
Gross loss	$ (8,039,000)	$ 2,866,000			$ (23,970,000)	$ 8,464,000	$ 3,639,000	$ (1,951,000)
Net loss	(22,916,000)	(2,840,000)	$ (59,792,000)	$ (3,356,000)	(82,707,000)	(6,196,000)	(15,924,000)	(13,495,000)
Share of net loss from equity method investment	$ (400)	$ (186,000)			$ (354,000)	$ (345,000)	1,399,000	(709,000)
Dimension Energy LLC
Statement of operations
Total revenue							22,570,000	0
Gross loss							17,360,000	0
Loss from operations							9,185,000	(3,413,000)
Net loss							5,933,000	(2,987,000)
Share of net loss from equity method investment							$ 1,399,000	$ (709,000)

- Definition

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 18: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1,2)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

+ Details

- Definition

Amount after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569616-111683

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 17: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 22: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

+ Details

Debt and Other Borrowings - Additional Information (Q3) (Details)						3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2021 USD ($)	Jan. 20, 2021 USD ($)	Apr. 30, 2020 USD ($)	Jun. 17, 2019 USD ($)	Jan. 30, 2017 USD ($) shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Mar. 31, 2020 shares
Debt Instrument [Line Items]
Common stock issued for notes purchased \| shares						84,944,145		84,944,145		66,155,340	63,633,981	9,162,976
Amortization of debt issuance cost						$ 200,000		$ 300,000
Gain (loss) on extinguishment of debt						0	$ (34,000)	790,000	$ (75,000)	$ (116,000)	$ 0
Interest expense on debt and other borrowings						$ 300,000	$ 100,000	500,000	$ 300,000	500,000	500,000
Barclays Bank PLC [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Initial margins	3.25%
Barclays Bank PLC [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Liquidity ratio amount, minimum limit								$ 125,000,000
Leverage ratio						3.75		3.75
Interest coverage ratio						1.5		1.5
Line of credit facility, covenant compliance								As of September 30, 2021, the Company was in full compliance with its financial condition covenant.
Revolving Line of Credit
Debt Instrument [Line Items]
Term of notes								3 years
Unamortized debt issuance cost						$ 1,800,000		$ 1,800,000
Credit facility revolver fees						100,000		200,000
Debt issuance costs						$ 2,100,000		$ 2,100,000
Revolving Line of Credit \| Western Alliance Bank [Member]
Debt Instrument [Line Items]
Principal amount				$ 1,000,000.0
Maturity period				2 years
Initial margins				5.50%
Line of credit, outstanding balance										$ 1,000,000.0	$ 1,000,000.0
Revolving Line of Credit \| Barclays Bank PLC [Member]
Debt Instrument [Line Items]
Principal amount	$ 100,000,000
Maturity period	3 years
Initial Commitment Fees	0.50%
Revolving Line of Credit \| Barclays Bank PLC [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Aggregate commitments	$ 100,000,000
Initial Commitment Fees	3.25%
Line of credit facility, covenant terms								The Credit Agreement includes the following financial condition covenants that the Company is required to satisfy: (i) maintain a minimum liquidity of $125 million for each quarter; (ii) maintain a 3.75 times leverage ratio; and (iii) maintain a 1.5 times interest coverage ratio. The leverage and interest coverage ratios will be triggered when the Company achieves $50 million in adjusted EBITDA over a trailing twelve months. Once the leverage and interest coverage ratios are triggered the minimum liquidity will not have a minimum limit. Minimum liquidity includes unrestricted cash plus the undrawn balance of the revolving credit facility. The minimum liquidity covenant was the only financial condition covenant the Company had to satisfy as of the period ended September 30, 2021.
The Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount of notes					$ 7,000,000
Term of notes					5 years
Common stock issued for notes purchased \| shares					25,000
Promissory notes purchased					$ 250,000
Interest rate of notes					5.00%
The Notes [Member] \| Private Placement [Member]
Debt Instrument [Line Items]
Aggregate principal amount of notes					$ 7,000,000.0
Term of notes					5 years
Common stock issued for notes purchased \| shares					25,000
Promissory notes purchased					$ 250,000
Interest rate of notes					5.00%
Paycheck Protection Program ('PPP') Loan [Member] \| CARES Act [Member]
Debt Instrument [Line Items]
Maturity period			2 years
Initial margins			1.00%
Loans received			$ 800,000
Gain (loss) on extinguishment of debt		$ 800,000

Commitments and Contingencies - Additional Information (Q3) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities [Member]
Product Warranty Liability [Line Items]
Warranty reserves	$ 1.2	$ 4.0	$ 1.4
Other Noncurrent Liabilities [Member]
Product Warranty Liability [Line Items]
Warranty reserves	$ 4.2	$ 2.8	$ 0.7

Commitments and Contingencies - Summary of Changes in Product Warranty Reserves (Q3) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Balance at beginning of period	$ 6,811	$ 2,057	$ 0
Warranties issued during the period	2,902	7,866	2,057
Settlements made during the period	(3,507)	(3,111)	0
Changes in liability for pre-existing warranties	(783)	(1)	0
Balance at end of period	$ 5,423	$ 6,811	$ 2,057

Stock-Based Compensation - Additional Information (Q3) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 5,400		$ 58,531	$ 1,381	$ 1,818	$ 906
Stock purchased and retired	2,191,557
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense						$ 0
Stock purchased and retired	2,263,827
Shares of Common stock purchased						9,900,000
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from IPO				241,200
Purchase cost of shares	$ 54,200			54,200
Retire aggregate shares of common stock	4,455,384
Stock-based compensation expense		5,400	$ 400	58,500	$ 1,400
IPO [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increased stock-based compensation expenses		$ 5,000		$ 57,100

Stockholders' Equity - Additional Information (Q3) (Details) - USD ($)						3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Apr. 30, 2021	Apr. 05, 2021	Jan. 08, 2021	Jul. 21, 2020	Jul. 21, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Apr. 28, 2021	Mar. 31, 2020
Class of Stock [Line Items]
Preferred Stock, Shares Authorized						10,000,000			10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share						$ 0.0001			$ 0.0001		$ 0.0001
Preferred Stock, Shares Issued						0			0		0
Common stock, shares authorized						850,000,000			850,000,000		98,960,064	98,960,064	98,960,064
Common stock, par value						$ 0.0001			$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Dividends									$ 0				$ 0
Common stock, shares issued						84,944,145			84,944,145		66,155,340	63,633,981			9,162,976
Sale of stock, price per share															$ 3.27
Common stock, value, issued						$ 8,000			$ 8,000		$ 1,000	$ 1,000			$ 30,000,024
Operating Expenses						14,732,000	$ 5,391,000		79,291,000	$ 14,051,000	20,565,000	10,420,000
Treasury stock, shares, acquired		717,460	148,440	9,896,666	9,896,666
Treasury stock, value		$ 0	$ 0	$ 0	$ 0	$ 0			$ 0		$ 0	$ 0
IPO [Member]
Class of Stock [Line Items]
Stock Issued During Period Shares New Issues	19,840,000								4,455,384
Shares Issued, Price Per Share	$ 13.00
Proceeds from Issuance Initial Public Offering	$ 241,200,000
Underwriting Discount and Commissions	$ 16,800,000
Sale of Stock, Consideration Received on Transaction								$ 54,200,000
IPO [Member] \| Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Stock Issued During Period Shares New Issues									2,263,827
IPO [Member] \| Repurchase [Member]
Class of Stock [Line Items]
Stock Issued During Period Shares New Issues									2,191,557

Net Loss Per Share (Additional Information) (Q3) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Net Loss Per Share [Abstract]
Forward stock split	8.25	8.25

Net Loss Per Share - Schedule of Computation of Basic and Diluted Loss Per Share (Q3) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Basic and diluted:
Net loss	$ (22,916)	$ (2,840)	$ (59,792)	$ (3,356)	$ (82,707)	$ (6,196)	$ (15,924)	$ (13,495)
Basic weighted-average number of common shares outstanding	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Diluted weighted-average number of common shares outstanding	94,596,519	67,567,724			82,677,824	69,857,468	68,810,533	62,043,383
Basic loss per share	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)
Diluted loss per share	$ (0.24)	$ (0.04)			$ (1.00)	$ (0.09)	$ (0.23)	$ (0.22)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Income Per Share (Q3) (Details) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	15,208	22,188	22,647,000	13,331,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	9,610	8,566	8,525,000	8,082,000
Restricted Stock Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share	5,598	13,622	14,122,000	5,249,000

Income Taxes - Additional Information (Q3) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Pre-tax income (loss) from company's operations	$ (22,875)	$ (2,630)	$ (82,216)	$ (5,966)	$ (17,406)	$ (12,825)
Income tax expense (benefit)	41	$ 24	$ 137	$ (115)	(83)	(39)
Change in deferred tax assets valuation allowance, percentage			21.00%
Unrecognized tax benefits	100		$ 100		81	45	$ 22
Income Tax Interest and Penalties Accrued	$ 0		$ 0		$ 0	$ 0

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123384075&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Segment Information - Additional Information (Q3) (Details) - Segment	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of operating segment	1	1
Non US [Member] \| Geographic Concentration Risk [Member] \| Total Revenue [Member] \| Maximum [Member]
Concentration Risk, Percentage		10.00%	10.00%

Segment Information - Schedule of Company's Total Revenue by Geographic Area (Q3) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Revenues	$ 52,989	$ 59,640	$ 168,804	$ 143,173	$ 187,352	$ 53,124
United States [Member]
Revenues	52,984	59,591	168,540	143,034	187,093	45,264
Vietnam [Member]
Revenues					38	7,149
Other [Member]
Revenues	$ 5	$ 49	$ 264	$ 139	$ 221	$ 711

- Definition

+ References

+ Details

Related Parties -Additional Information (Q3) (Details) - USD ($)	Jun. 29, 2021	Apr. 05, 2021	Jan. 08, 2021	Jul. 21, 2020	Jul. 21, 2020	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Treasury stock, shares, acquired		717,460	148,440	9,896,666	9,896,666
Treasury stock, value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Two Executive Member [Member]
Related Party Transaction [Line Items]
Payment Of Success Based Fee	$ 1,900,000