Proterra (PTRAQ) 10-Q 3 Nov 22 2022 Q3 Quarterly report Financial data

Cover

Cover - shares shares in Millions	9 Months Ended
	Sep. 30, 2022	Oct. 31, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	001-39546
Entity Registrant Name	Proterra Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-1551379
Entity Address, Address Line One	1815 Rollins Road
Entity Address, City or Town	Burlingame
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94010
City Area Code	864
Local Phone Number	438-0000
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	PTRA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		225.5
Entity Central Index Key	0001820630
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Cash and cash equivalents	$ 59,610	$ 170,039
Accounts receivable, net	102,361	81,644
Short-term investments	348,938	490,967
Inventory	164,834	114,556
Prepaid expenses and other current assets	28,731	15,300
Deferred cost of goods sold	3,578	1,816
Restricted cash, current	12,105	12,105
Total current assets	720,157	886,427
Property, plant, and equipment, net	93,656	62,246
Operating lease right-of-use assets	24,169	24,282
Restricted cash, non-current	460	460
Long-term prepayment	10,000	0
Other assets	36,453	8,472
Total assets	884,895	981,887
Liabilities and Stockholders’ Equity:
Accounts payable	69,938	53,404
Accrued liabilities	25,919	20,634
Deferred revenue, current	11,815	13,821
Operating lease liabilities, current	6,354	4,084
Total current liabilities	114,026	91,943
Debt, non-current	116,995	110,999
Deferred revenue, non-current	29,692	22,585
Operating lease liabilities, non-current	18,992	20,963
Other long-term liabilities	16,695	15,245
Total liabilities	296,400	261,735
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.0001 par value; 500,000 shares authorized and 225,532 shares issued and outstanding as of September 30, 2022 (unaudited); 500,000 shares authorized and 221,960 shares issued and outstanding as of December 31, 2021	22	22
Preferred stock, $0.0001 par value; 10,000 shares authorized and zero shares issued and outstanding as of September 30, 2022 (unaudited); 10,000 shares authorized, zero shares issued and outstanding as of December 31, 2021	0	0
Additional paid-in capital	1,605,727	1,578,943
Accumulated deficit	(1,015,185)	(858,225)
Accumulated other comprehensive loss	(2,069)	(588)
Total stockholders’ equity	588,495	720,152
Total liabilities and stockholders’ equity	$ 884,895	$ 981,887

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	225,532,429	221,960,000
Common stock, shares outstanding (in shares)	225,532,429	221,960,000
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Total revenue	$ 96,223	$ 61,941	$ 229,368	$ 174,449
Total cost of goods sold	97,499	59,278	233,092	169,602
Gross profit (loss)	(1,276)	2,663	(3,724)	4,847
Research and development	18,165	11,296	44,871	31,311
Selling, general and administrative	38,554	21,123	98,646	60,327
Total operating expenses	56,719	32,419	143,517	91,638
Loss from operations	(57,995)	(29,756)	(147,241)	(86,791)
Interest expense, net	7,361	6,362	21,191	44,288
Gain on debt extinguishment	0	0	(10,201)	0
(Gain) loss on valuation of derivative and warrant liabilities	0	(73,197)	0	72,913
Other expense (income), net	(295)	758	(1,271)	876
Income (loss) before income taxes	(65,061)	36,321	(156,960)	(204,868)
Provision for income taxes	0	0	0	0
Net income (loss)	$ (65,061)	$ 36,321	$ (156,960)	$ (204,868)
Net income (loss) per share of common stock:
Basic (in dollars per share)	$ (0.29)	$ 0.17	$ (0.70)	$ (2.30)
Diluted (in dollars per share)	$ (0.45)	$ (0.42)	$ (0.79)	$ (2.30)
Weighted average shares used in per share computation:
Basic (in shares)	225,291	212,071	223,782	89,233
Diluted (in shares)	250,704	236,965	248,637	89,233
Product
Total revenue	$ 89,769	$ 59,907	$ 214,196	$ 167,401
Total cost of goods sold	91,408	57,034	217,743	162,513
Parts and other service
Total revenue	6,454	2,034	15,172	7,048
Total cost of goods sold	$ 6,091	$ 2,244	$ 15,349	$ 7,089

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (65,061)	$ 36,321	$ (156,960)	$ (204,868)
Available-for-sales securities:
Unrealized gain (loss) on available-for-sale securities	625	0	(1,481)	0
Other comprehensive income (loss), net of taxes	625	0	(1,481)	0
Total comprehensive income (loss), net of taxes	$ (64,436)	$ 36,321	$ (158,441)	$ (204,868)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2020		115,136	5,678
Beginning balance at Dec. 31, 2020	$ 74,466	$ 13	$ 1	$ 682,671	$ (608,219)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock upon exercise of options and warrants (in shares)			3,241
Issuance of stock upon exercise of options and warrants	5,468			5,468
Conversion of convertible preferred stock into common stock in connection with the reverse recapitalization (in shares)		(115,136)	115,576
Conversion of convertible preferred stock into common stock in connection with the reverse recapitalization	0	$ (13)	$ 11	2
Conversion of Convertible Notes into common stock (in shares)			7,424
Conversion of Convertible Notes into common stock	48,781		$ 1	48,780
Issuance of common stock upon the reverse recapitalization, net of issuance costs (in shares)			76,172
Issuance of common stock upon the reverse recapitalization, net of issuance costs	502,315		$ 8	502,307
Reclassification of derivative liability upon the reverse recapitalization	182,554			182,554
Reclassification of Legacy Proterra warrant liability upon the reverse recapitalization	87,016			87,016
Issuance of Earnout Shares, net of repurchase (in shares)			4,736
Issuance of Earnout Shares, net of repurchase	(634)			(634)
Stock-based compensation	11,265			11,265
Net income (loss)	(204,868)				(204,868)
Other comprehensive gain (loss), net of taxes	0
Ending balance (in shares) at Sep. 30, 2021		0	212,827
Ending balance at Sep. 30, 2021	706,363	$ 0	$ 21	1,519,429	(813,087)	0
Beginning balance (in shares) at Jun. 30, 2021		0	207,621
Beginning balance at Jun. 30, 2021	665,944	$ 0	$ 21	1,515,331	(849,408)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock upon exercise of options and warrants (in shares)			470
Issuance of stock upon exercise of options and warrants	1,666			1,666
Issuance of common stock upon the reverse recapitalization, net of issuance costs	(112)			(112)
Issuance of Earnout Shares, net of repurchase (in shares)			4,736
Issuance of Earnout Shares, net of repurchase	(634)			(634)
Stock-based compensation	3,178			3,178
Net income (loss)	36,321				36,321
Other comprehensive gain (loss), net of taxes	0
Ending balance (in shares) at Sep. 30, 2021		0	212,827
Ending balance at Sep. 30, 2021	706,363	$ 0	$ 21	1,519,429	(813,087)	0
Beginning balance (in shares) at Dec. 31, 2021		0	221,960
Beginning balance at Dec. 31, 2021	720,152	$ 0	$ 22	1,578,943	(858,225)	(588)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock upon exercise of options and warrants (in shares)			3,247
Issuance of stock upon exercise of options and warrants	8,969			8,969
Stock issuance for employee stock purchase plan (in shares)			325
Stock issuance for employee stock purchase plan	1,502			1,502
Stock-based compensation	16,313			16,313
Net income (loss)	(156,960)				(156,960)
Other comprehensive gain (loss), net of taxes	(1,481)					(1,481)
Ending balance (in shares) at Sep. 30, 2022		0	225,532
Ending balance at Sep. 30, 2022	588,495	$ 0	$ 22	1,605,727	(1,015,185)	(2,069)
Beginning balance (in shares) at Jun. 30, 2022		0	224,979
Beginning balance at Jun. 30, 2022	646,450	$ 0	$ 22	1,599,246	(950,124)	(2,694)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock upon exercise of options and warrants (in shares)			553
Issuance of stock upon exercise of options and warrants	1,125			1,125
Stock-based compensation	5,356			5,356
Net income (loss)	(65,061)				(65,061)
Other comprehensive gain (loss), net of taxes	625					625
Ending balance (in shares) at Sep. 30, 2022		0	225,532
Ending balance at Sep. 30, 2022	$ 588,495	$ 0	$ 22	$ 1,605,727	$ (1,015,185)	$ (2,069)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net loss	$ (156,960)	$ (204,868)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	9,583	11,675
Loss on disposal of fixed assets	169	411
Stock-based compensation	16,313	11,265
Amortization of debt discount and issuance costs	10,497	31,519
Accretion of debt end of term charge and PIK interest	5,559	6,375
Gain on debt extinguishment	(10,007)	0
Loss on valuation of derivative and warrant liabilities	0	72,913
Others	(857)	991
Changes in operating assets and liabilities:
Accounts receivable	(20,717)	(8,223)
Inventory	(49,762)	(9,622)
Prepaid expenses and other current assets	(13,508)	(5,231)
Deferred cost of goods sold	(1,761)	175
Operating lease right-of-use assets and liabilities	412	(84)
Other assets	(13,042)	(1,785)
Accounts payable and accrued liabilities	19,922	21,977
Deferred revenue, current and non-current	5,100	(673)
Other non-current liabilities	1,473	934
Net cash used in operating activities	(197,586)	(72,251)
Cash flows from investing activities:
Purchase of investments	(395,596)	(472,953)
Proceeds from maturities of investments	512,000	94,000
Purchase of property and equipment	(41,833)	(12,912)
Net cash provided by (used in) investing activities	74,571	(391,865)
Cash flows from financing activities:
Merger and PIPE financing	0	644,809
Payment of tax withholding obligations on earnout Shares	0	(634)
Repayment of debt	0	(17,083)
Proceeds from (repayment of) government grants	(700)	1,323
Proceeds from exercise of stock options and warrants	8,969	5,468
Proceeds from employee stock purchase plan	1,502	0
Other financing activities	2,815	(362)
Net cash provided by financing activities	12,586	633,521
Net increase (decrease) in cash and cash equivalents, and restricted cash	(110,429)	169,405
Cash and cash equivalents, and restricted cash at the beginning of period	182,604	123,697
Cash and cash equivalents, and restricted cash at the end of period	72,175	293,102
Supplemental disclosures of cash flow information:
Cash paid for interest	6,289	4,912
Cash paid for income taxes	0	0
Non-cash investing and financing activity:
Assets acquired through accounts payable and accrued liabilities	4,798	1,532
Non-cash transfer of assets to inventory	515	743
Reclassification of Convertible Notes warrants liability upon exercise	0	17,696
Conversion of Convertible Notes into common stock	0	48,607
Reclassification of remaining Convertible Notes warrants liability upon the reverse recapitalization	0	69,320
Reclassification of derivative liability upon the reverse recapitalization	0	182,554
Conversion of convertible preferred stock into common stock	$ 0	$ 627,315

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Organization and Description of Business Proterra Inc (“Proterra”), formerly known as ArcLight Clean Transition Corp. (“ArcLight”), is a leading developer and producer of electric vehicle technology for commercial applications. Proterra designs, develops, manufactures, and sells electric transit buses as an original equipment manufacturer for North American public transit agencies, airports, universities, and other commercial transit fleets. It also designs, develops, manufactures, sells, and integrates proprietary battery systems and electrification solutions for global commercial vehicle manufacturers. Additionally, Proterra provides fleet-scale, high-power charging solutions for its customers. Legacy Proterra (as defined below) was originally formed in June 2004 as a Colorado limited liability company and converted to a Delaware corporation in February 2010. Proterra operates from its headquarters and battery production facility in Burlingame, California. Proterra also has manufacturing and product development facilities in Greenville and Greer, South Carolina and City of Industry, California. On June 11, 2021, ArcLight filed a notice of deregistration with the Cayman Islands Registrar of Companies, and filed a certificate of incorporation and a certificate of corporate domestication with the Secretary of State of the State of Delaware, under which ArcLight was domesticated and continued as a Delaware corporation. On June 14, 2021 (the “Closing Date”), ArcLight consummated a merger with Phoenix Merger Sub, Inc., a Delaware corporation and a wholly-owned subsidiary of ArcLight (“Phoenix Merger Sub”), and Proterra Inc, a Delaware corporation (“Legacy Proterra”), with Legacy Proterra surviving as the surviving company and as a wholly-owned subsidiary of ArcLight (the “Merger” and, collectively with the other transactions described in the Agreement and Plan of Merger (the “Merger Agreement”), the “Business Combination”). In connection with the Business Combination, Legacy Proterra changed its name to “Proterra Operating Company, Inc.” and ArcLight changed its name to “Proterra Inc”. The Merger was accounted for as a reverse merger and a recapitalization with Legacy Proterra being the accounting acquirer. Accordingly, all historical financial information presented in the unaudited condensed consolidated financial statements of Proterra represents the accounts of Legacy Proterra and its wholly owned subsidiaries as if Legacy Proterra is the predecessor to Proterra. The shares and net loss per common share, prior to the Merger, have been retroactively restated as shares reflecting the exchange ratio established in the Merger (0.8925 shares of Legacy Proterra common stock for 1 share of Proterra common stock) (the “Exchange Ratio”). Unless otherwise specified or unless the context otherwise requires, references in these notes to the “Company,” “we,” “us,” or “our” refer to Legacy Proterra prior to the Business Combination and to Proterra following the Business Combination. Prior to the closing of the Business Combination (the “Closing”), ArcLight’s Class A ordinary shares and public warrants were listed on the Nasdaq Capital Market under the symbols “ACTC” and “ACTCW,” respectively. Proterra’s common stock is currently listed on the Nasdaq Global Select Market under the symbol “PTRA”. See Note 3 “Reverse Recapitalization” for further details of the Merger. The Company’s public warrants were previously listed on the Nasdaq Global Select Market under the symbol “PTRAW.” On October 29, 2021, the Company redeemed its remaining outstanding public warrants at a redemption price of $0.10 per public warrant. The Company has incurred net losses and negative cash flows from operations since inception. As of September 30, 2022, the Company has an accumulated deficit of $1.0 billion. The Company has $408.5 million of cash and cash equivalents and short-term investments as of September 30, 2022. The Company has funded operations primarily through a combination of equity and debt financing. Management believes that the Company’s currently available resources will be sufficient to fund its cash requirements for at least the next twelve months. However, there can be no assurance that future financings will be successfully completed or completed on terms acceptable to the Company. Global economic conditions have been worsening, with disruptions to, and volatility in, the credit and financial markets in the U.S. and worldwide. If these conditions persist, the Company’s ability to access additional capital or our liquidity could be impacted. If the Company is unable to raise capital when needed or on attractive terms, the Company would be forced to delay, reduce or eliminate our research and development programs and/or other efforts. These financial statements do not include any adjustments that may result from the outcome of this uncertainty. Basis of Presentation The unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”). The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation. Certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2021 and the related notes incorporated by referenced in the Company’s Annual Report (the “Annual Report”) on Form 10-K, filed with SEC on March 14, 2022, which provides a more complete discussion of the Company’s accounting policies and certain other information. The information as of December 31, 2021 and 2020 was derived from the Company’s audited financial statements. The condensed consolidated financial statements were prepared on the same basis as the audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for a fair presentation of the Company’s financial position as of September 30, 2022 and the results of operations and cash flows for the three and nine months ended September 30, 2022 and 2021. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results that may be expected for the year ending December 31, 2022. Use of Estimates In preparing the condensed consolidated financial statements and related disclosures in conformity with U.S. GAAP and pursuant to the rules and regulations of the SEC, the Company must make estimates and judgments that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results may differ materially from these estimates. Significant Accounting Policies There have been no material changes to the Company’s significant accounting policies described in the Annual Report. The Company has not experienced any significant impact to estimates or assumptions as a result of the COVID-19 pandemic. However, the Company’s financial results have been impacted by ongoing constraints and inefficiencies in production largely driven by shortages of component parts and shipment delays, and workforce absences due to illness or quarantines during the pandemic experienced by the Company or its suppliers. The Company will continue to monitor impacts of the COVID-19 pandemic on an ongoing basis. While the COVID-19 pandemic has not had a material adverse impact on the Company’s financial condition and results of operations to date, the gravity of the impact of the COVID-19 pandemic and related macroeconomic and geopolitical conditions on the Company’s future operational and financial performance will depend on certain developments, including the duration of the pandemic and spread of COVID-19 (including the variant strains of the virus), the impact on the Company’s customers and the effect on the Company’s suppliers, all of which are uncertain and cannot be predicted. Segments The Company operates in the United States and has sales to the European Union, Canada, United Kingdom, Australia, Japan and Turkey. Revenue disaggregated by geography, based on the addresses of the Company’s customers, consists of the following (in Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 United States $ 82,040 $ 59,482 $ 195,680 $ 163,972 Rest of World 14,183 2,459 33,688 10,477 96,223 61,941 $ 229,368 $ 174,449 The Company’s chief operating decision maker is its Chief Executive Officer, who reviews financial information presented at the entity level. Accordingly, the Company has determined that it has a single reportable segment. Accounts Receivable and Allowance for Credit Losses Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company determines the allowance for credit losses based on historical write-off experience, an analysis of the aging of outstanding receivables, customer payment patterns and expectations of changes in macroeconomic conditions that may affect the collectability of outstanding receivables. The allowance for credit losses was not material as of September 30, 2022 and December 31, 2021. Credit Risk and Concentration The Company’s financial instruments that are potentially subject to concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, short-term investments, and accounts receivable. Cash and cash equivalents and short-term investments are maintained primarily at one financial institution as of September 30, 2022, and deposits exceed federally insured limits. Risks associated with cash and cash equivalents, and short-term investments are mitigated by banking with creditworthy financial institutions. The Company has not experienced any losses on its deposits of cash and cash equivalents or its short-term investments. Cash equivalents and short-term investments consist of short-term money market funds, corporate debt securities, and debt securities issued by the U.S. Treasury, which are deposited with reputable financial institutions. The Company’s cash management and investment policy limits investment instruments to securities with short-term credit ratings at the timing of purchase of P-2 and A-2 or better from Moody’s Investors Service and Standard & Poor’s Financial Services, LLC, respectively, with the objective to preserve capital and to maintain liquidity until the funds can be used in business operations. Accounts receivable are typically unsecured and are generally derived from revenue earned from transit agencies, universities and airports in North America and global commercial vehicle manufacturers in North America, the European Union, the United Kingdom, Australia, Japan and Turkey. The Company periodically evaluates the collectability of its accounts receivable and provides an allowance for potential credit losses as necessary. Given the large order value for customers and the relatively low number of customers, revenue and accounts receivable have typically been concentrated with a limited number of customers. Revenue Accounts Receivable Three Months Ended September 30, Nine Months Ended September 30, September 30, December 31, 2022 2021 2022 2021 2022 2021 Number of customers accounted for 10% or more 2 2 2 — 2 1 Total % for customers accounted for 10% or more 40 % 30 % 27 % — % 40 % 18 % Single source suppliers provide the Company with a number of components that are required for manufacturing of its current products. In other instances, although there may be multiple suppliers available, many of the components are purchased from one single source. If these single source suppliers fail to meet the Company’s requirements on a timely basis at competitive prices or are unable to provide components for any reason, the Company could suffer manufacturing delays, a possible loss of revenue, or incur higher cost of sales, any of which could adversely impact the Company’s operating results. Impairment of Long-Lived Assets The Company evaluates the recoverability of property, plant, and equipment and right-of-use assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review indicates that the carrying amount of long-lived assets is not recoverable, the carrying amount of such assets is reduced to fair value. In addition to the recoverability assessment, the Company periodically reviews the remaining estimated useful lives of property, plant, and equipment. If the estimated useful life assumption for any asset is reduced, the remaining net book value is depreciated over the revised estimated useful life. The Company reviews long-lived assets for impairment at the lowest level for which separate cash flows can be identified. No impairment charge was recognized in the three and nine months ended September 30, 2022 and 2021. Deferred Revenue Deferred revenue consists of billings or payments received in advance of revenue recognition that are recognized as revenue once the revenue recognition criteria are met. In some instances, progress billings are issued upon meeting certain milestones stated in the contracts. Accordingly, the deferred revenue balance does not represent the total contract value of non-cancelable arrangements. Invoices are typically due within 30 to 40 days. The changes in deferred revenue consisted of the following (in thousands): Deferred revenue as of December 31, 2021 $ 36,406 Revenue recognized from beginning balance during the nine months ended September 30, 2022 (10,972) Deferred revenue added during the nine months ended September 30, 2022 16,073 Deferred revenue as of September 30, 2022 $ 41,507 The current portion of deferred revenue represents the amount that is expected to be recognized as revenue within one year from the balance sheet date. Revenue Recognition The Company derives revenue primarily from the sale of vehicles and charging systems, the installation of charging systems, the sale of battery systems and powertrain components to other vehicle manufacturers, as well as the sale of spare parts and other services provided to customers. Product revenue consists of revenue earned from vehicles and charging systems, battery systems and powertrain components, installation of charging systems, and revenue from leased vehicles, charging systems, and batteries under operating leases. Leasing revenue recognized over time was approximately $0.2 million and $0.5 million in the three months ended September 30, 2022 and 2021, respectively, and $0.9 million and $1.6 million in the nine months ended September 30, 2022 and 2021, respectively. Parts and other service revenue includes revenue earned from spare parts, the design and development of battery systems and powertrain systems for other vehicle manufacturers, and extended warranties. The Company recognizes revenue when or as it satisfies a performance obligation by transferring control of a product or service to a customer. Revenue from product sales is recognized when control of the underlying performance obligations is transferred to the customer. Revenue from sales of vehicles is typically recognized upon delivery when the Company can objectively demonstrate that the criteria specified in the contractual acceptance provisions are achieved prior to delivery. In cases, where the Company cannot objectively demonstrate that the criteria specified in the contractual acceptance provisions have been achieved prior to delivery, revenue is recognized upon acceptance by the customer. Revenue from sales of charging systems is recognized at a point in time, generally upon delivery or commissioning when control of the underlying performance obligations are transferred to the customer. Under certain contract arrangements, the control of the performance obligations related to the charging systems is transferred over time, and the associated revenue is recognized over the installation period using an input measure based on costs incurred to date relative to total estimated costs to completion. Spare parts revenue is recognized upon shipment. Extended warranty revenue is recognized over the life of the extended warranty using the time elapsed method. Development service contracts typically include the delivery of prototype products to customers. The performance obligation associated with the development of prototype products as well as battery systems and powertrain components to other vehicle manufacturers, is satisfied at a point in time, typically upon shipping. Revenue derived from performance obligations satisfied over time from charging systems and installation was $3.7 million and $0.2 million for the three months ended September 30, 2022 and 2021, respectively, and $5.8 million and $5.3 million for the nine months ended September 30, 2022 and 2021, respectively. Extended warranty revenue was $0.4 million and $0.6 million for the three months ended September 30, 2022 and 2021, respectively, and $1.5 million and $1.3 million for the nine months ended September 30, 2022 and 2021, respectively. As of September 30, 2022 and December 31, 2021, the contract assets balance was $10.2 million and $1.3 million, respectively. The contract assets are expected to be billed within the next twelve months and are recorded in prepaid expenses and other current assets on the Company’s balance sheets. As of September 30, 2022, the amount of remaining performance obligations that have not been recognized as revenue was $413.8 million, of which 85% were expected to be recognized as revenue over the next 12 months and the remainder thereafter. This amount excludes the value of remaining performance obligations for contracts with an original expected length of one year or less. Our business is organized into two business units with three business lines, each of which addresses a critical component of the commercial vehicle electrification value proposition in a complementary and self-reinforcing manner: • Proterra Transit designs, develops, manufactures, and sells electric transit buses as an original equipment manufacturer (“OEM”) for North American public transit agencies, airports, universities, and other commercial transit fleets. • Proterra Powered & Energy includes Proterra Powered, which designs, develops, manufactures, sells, and integrates proprietary battery systems and electrification solutions into vehicles for global commercial vehicle OEMs, and Proterra Energy, which provides turnkey fleet-scale, high-power charging solutions and software services, ranging from fleet and energy management software-as-a-service, to fleet planning, hardware, infrastructure, installation, utility engagement, and charging optimization. The revenue of business units are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Proterra Transit $ 56,363 $ 50,175 $ 142,563 $ 140,187 Proterra Powered & Energy 39,860 11,766 86,805 34,262 Total $ 96,223 $ 61,941 $ 229,368 $ 174,449 Product Warranties Warranty expense is recorded as a component of cost of goods sold. Accrued warranty activity consisted of the following (in thousands): Nine Months Ended September 30, 2022 Warranty reserve - beginning of period $ 23,274 Warranty costs incurred (6,759) Net changes in liability for pre-existing warranties, including expirations (2,625) Provision for warranty 11,153 Warranty reserve - end of period $ 25,043

Adoption of New Accounting Stan

Adoption of New Accounting Standards	9 Months Ended
	Sep. 30, 2022
Accounting Changes and Error Corrections [Abstract]
Adoption of New Accounting Standards	Adoption of New Accounting Standards ASU No. 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity . This standard simplifies the accounting for convertible instruments by removing certain separation models in ASC 470- 20, Debt—Debt with Conversion and Other Options . This standard updates the guidance on certain embedded conversion features that are not required to be accounted for as derivatives under Topic 815, Derivatives and Hedging , or that do not result in substantial premiums accounted for as paid-in capital, such that those features are no longer required to be separated from the host contract. The convertible debt instruments will be accounted for as a single liability measured at amortized cost. This will also result in the interest expense recognized for convertible debt instruments to be typically closer to the coupon interest rate when applying the guidance in Topic 835, Interest . Further, this standard made amendments to the EPS guidance in Topic 260 for convertible instruments, the most significant impact of which is requiring the use of the if-converted method for diluted earnings per share calculation, and no longer allowing the net share settlement method. This standard also made revisions to Topic 815-40, which provides guidance on how an entity must determine whether a contract qualifies for a scope exception from derivative accounting. The amendments to Topic 815-40 change the scope of contracts that are recognized as assets or liabilities. The Company adopted this standard on January 1, 2022, and it had no material impact on the condensed consolidated financial statements.

Reverse Recapitalization

Reverse Recapitalization	9 Months Ended
	Sep. 30, 2022
Reverse Recapitalization [Abstract]
Reverse Recapitalization	Reverse Recapitalization On June 14, 2021, Phoenix Merger Sub merged with Legacy Proterra, with Legacy Proterra surviving as a wholly-owned subsidiary of ArcLight. In connection with the Business Combination, Legacy Proterra changed its name to “Proterra Operating Company, Inc.” and ArcLight changed its name to “Proterra Inc”. The following transactions occurred upon the Closing: • each share of outstanding Legacy Proterra convertible preferred stock was converted into shares of Proterra common stock in accordance with the applicable conversion ratio immediately prior to the effective time, and each share of Legacy Proterra common stock (including shares issued upon conversion of Legacy Proterra convertible preferred stock and warrants net exercised upon Closing) was converted into shares of common stock after giving effect to the Exchange Ratio of 0.8925 and resulting in the issuance of 123,752,882 shares of common stock; • certain holders of Convertible Notes (as defined in Note 6 “Debt”) with an original aggregate principal amounts of $46.5 million elected to convert their outstanding Convertible Notes balances including accrued PIK interest and cash interest at the Closing resulting in the issuance of 7.4 million shares of common stock; • each outstanding Legacy Proterra option was converted into an option to purchase shares of Proterra common stock by multiplying the number of underlying shares by the Exchange Ratio, rounded down to the nearest whole share, resulting in such options being exercisable to purchase for an aggregate of 22,532,619 shares of Proterra common stock; the exercise price of each converted option was determined by dividing the per share exercise price of the respective Legacy Proterra options by the Exchange Ratio of 0.8925, rounded up to the nearest whole cent; • each outstanding Legacy Proterra warrant to purchase Legacy Proterra common stock and convertible preferred stock was converted into a warrant to purchase shares of Proterra common stock by multiplying the number of underlying shares by the Exchange Ratio, rounded down to the nearest whole share, resulting in such warrants being exercisable to purchase an aggregate of 3,504,523 shares of Proterra common stock; the exercise price of each converted warrant will be determined by dividing the per share exercise price of the respective Legacy Proterra warrant by the Exchange Ratio of 0.8925, rounded up to the nearest whole cent; • each outstanding Convertible Note that was not optionally converted in connection with the Closing remained outstanding and became convertible into shares of Proterra common stock in accordance with the terms of such Convertible Notes; • 15,172 public shares were redeemed by ArcLight shareholders, and an aggregate of $0.2 million was paid from the trust account to these redeeming holders; and each ArcLight Class A and Class B ordinary share was converted into the right to receive one share of Proterra’s common stock resulting in the issuance of 34,671,900 shares of common stock; • pursuant to the subscription agreements between ArcLight and certain investors (the “PIPE Investors”), the PIPE Investors purchased 41.5 million shares of Proterra common stock at a purchase price of $10.00 per share for aggregate gross proceeds of $415.0 million (the “PIPE Financing”); • each ArcLight warrant outstanding immediately prior to the consummation was converted into a warrant exercisable into an equivalent number of shares of Proterra common stock, resulting in such warrants being exercisable for an aggregate of 21,424,994 shares of Proterra common stock; and • the 669,375 shares of Proterra common stock underlying certain Milestone Options (as defined below) fully vested upon the Closing. Upon the occurrence of any of the following events during the first five years following the Closing (“earnout period”), up to an additional 22,809,500 shares of Proterra common stock (the “Earnout Stock”) may be issued to former holders of Legacy Proterra convertible preferred stock, common stock, warrants, vested options and Convertible Notes as of immediately prior to the Closing, as follows: a. 21.0526% of the Earnout Stock if over any 20 trading days within any 30 trading day period, the volume-weighted average price (“VWAP”) of the Proterra common stock is greater than or equal to $15.00 per share or there occurs any transaction resulting in a change in control with a valuation of the Proterra common stock that is greater than or equal to $15.00 per share (the “First Earnout Shares”); b. an additional 26.3158% of the Earnout Stock if over any 20 trading days within any 30 trading day period, the VWAP of the Proterra common stock is greater than or equal to $20.00 per share or there occurs any transaction resulting in a change in control with a valuation of the Proterra common stock that is greater than or equal to $20.00 per share; c. an additional 26.3158% of the Earnout Stock if over any 20 trading days within any 30 trading day period, the VWAP of the Proterra common stock is greater than or equal to $25.00 per share or there occurs any transaction resulting in a change in control with a valuation of the Proterra common stock that is greater than or equal to $25.00 per share; and d. an additional 26.3158% of the Earnout Stock if over any 20 trading days within any 30 trading day period, the VWAP of the Proterra common stock is greater than or equal to $30.00 per share or there occurs any transaction resulting in a change in control with a valuation of the Proterra common stock that is greater than or equal to $30.00 per share. Pursuant to a letter agreement with ArcLight CTC Holdings, L.P. (the “Sponsor”), 10% of the Proterra common stock received by the Sponsor upon consummation of the Merger in exchange for its outstanding ArcLight Class B ordinary shares, excluding 140,000 shares owned by the ArcLight board of directors (the “ArcLight Board”), was subject to vesting and forfeiture (the “Sponsor Earnout Stock”). Such shares of Sponsor Earnout Stock would vest if over any 20 trading days within any 30 trading day period during the five-year earnout period, the VWAP of the Proterra common stock was greater than or equal to $15.00 per share or there occurred any transaction resulting in a change in control with a valuation of the Proterra common stock that is greater than or equal to $15.00 per share. In July 2021, the conditions for the issuance of the First Earnout Shares and the vesting of the Sponsor Earnout Stock were satisfied, resulting in an aggregate of 4,800,563 shares of common stock being issued and the 679,750 shares of Sponsor Earnout Stock fully vesting. The Earnout Stock and Sponsor Earnout Stock met indexation and other criteria under Topic 815, Derivatives and Hedging, and are considered as equity-classified instruments. The number of shares of Proterra common stock issued immediately following the consummation of the Merger was (in thousands): Shares ArcLight Class A ordinary shares, outstanding prior to Merger 27,750 Less redemption of ArcLight shares (15) Sponsor 6,257 Sponsor Earnout Stock 680 Common stock of ArcLight 34,672 PIPE Investors 41,500 Legacy Proterra shares 131,176 Total shares of common stock immediately after Merger 207,348 Immediately after the Merger, Proterra is authorized to issue 510.0 million shares, with a par value of $0.0001 per share. As of the Closing, the authorized shares consisted of 500.0 million shares of common stock and 10.0 million shares of preferred stock, and there were 207.3 million shares of common stock issued and outstanding, and no shares of preferred stock issued and outstanding. In addition, as of the Closing, there were 24.9 million warrants issued and outstanding, including 13.9 million public warrants, 7.6 million private placement warrants, and 3.5 million Legacy Proterra warrants. As of the Closing, a total of 82.3 million shares were reserved for future issuance upon the exercise of stock options, warrants and the issuance of Earnout Stock, of which 10.4 million shares were reserved for issuance under Proterra’s 2021 Equity Incentive Plan, 22.5 million shares were reserved under Legacy Proterra’s 2010 Equity Incentive Plan and 1.6 million shares reserved under Proterra’s 2021 Employee Stock Purchase Plan. The Merger has been accounted for as a reverse merger and a recapitalization under U.S. GAAP with Legacy Proterra being the accounting acquirer, based on evaluation of the following facts and circumstances: • Legacy Proterra’s stockholders have a majority of the voting power of Proterra following the Merger; • Legacy Proterra initially designated a majority of the board of directors of Proterra (the “Board”); • Legacy Proterra’s management comprised the management of Proterra; • Legacy Proterra comprised the ongoing operations of Proterra; • Legacy Proterra was the larger entity based on historical revenues and business operations; and • Proterra assumed Legacy Proterra’s name. Under this method of accounting, ArcLight is treated as the “acquired” company for accounting and financial reporting purposes. Accordingly, for accounting purposes, this merger transaction is treated as the equivalent of Legacy Proterra issuing equity for the net assets of ArcLight, accompanied by a recapitalization. The net assets of ArcLight have been stated at historical cost, with no goodwill or other intangible assets recorded.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company measures certain financial assets and liabilities at fair value. Fair value is determined based on the exit price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value is estimated by applying the following hierarchy: Level 1 – Quoted prices in active markets for identical assets or liabilities; Level 2 – Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 – Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Financial assets measured at fair value on a recurring basis using the above input categories were as follows (in thousands): Pricing Category Fair Value at September 30, 2022 December 31, 2021 Assets: Cash equivalents and marketable securities: Money market funds Level 1 $ 44,696 $ 102,978 U.S. Treasury securities Level 1 7,962 49,996 Short-term investments: U.S. Treasury securities Level 1 348,938 330,053 Corporate debt securities Level 2 — 160,914 Total $ 401,596 $ 643,941 The Company’s short-term investments were primarily comprised of U.S. Treasury and corporate debt securities, and classified as available-for-sale at the time of purchase because it is intended that these investments are available for current operations. Investments are reported at fair value and are subject to periodic impairment review. Unrealized gains and losses related to changes in the fair value of these securities are recognized in accumulated other comprehensive loss. The ultimate value realized on these securities is subject to market price volatility until they are sold. Realized gains or losses from short-term investments are recorded in other expense (income), net. As of September 30, 2022, the Company has $26.6 million of long-term investments recorded in other assets in the condensed consolidated balance sheets, comprised of minority ownership of equity investments in privately held entities. In the third quarter of 2022, the Company made a $25.0 million strategic equity investment in an entity that the Company expects to produce lithium iron phosphate (LFP) battery cells in the United States in the coming years which will provide the Company with development opportunities for battery packs with another cell chemistry to address additional segments of the commercial vehicle market. These investments do not have a readily determinable fair value and are accounted for under a measurement alternative at cost, less impairment, adjusted for observable price changes. No impairment charges or observable price changes were recognized in the three and nine months ended September 30, 2022 and 2021. There are no unrealized gains or losses associated with these investments as of September 30, 2022. The following is a summary of cash equivalents and marketable securities as of September 30, 2022 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 44,696 $ — $ 44,696 U.S. Treasury securities 7,962 — 7,962 Short-term investments: U.S. Treasury securities 351,007 (2,069) 348,938 Total $ 403,665 $ (2,069) $ 401,596 As of September 30, 2022, the contractual maturities of the short-term investments were less than one year. The following is a summary of cash equivalents and marketable securities as of December 31, 2021 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 102,978 $ — $ 102,978 U.S. Treasury securities 49,996 — 49,996 Short-term investments: U.S. Treasury securities 330,618 (565) 330,053 Corporate debt securities 160,937 (23) 160,914 Total $ 644,529 $ (588) $ 643,941 The unrealized losses as of September 30, 2022 and December 31, 2021 were primarily related to U.S. Treasury securities with original maturities longer than one year due to recent changes in interest rates and are considered temporary in nature. The fair value of the Convertible Notes was $213.6 million as of September 30, 2022. The carrying value of the Convertible Notes of $117.0 million, net of $51.9 million unamortized debt discount and issuance costs, as of September 30, 2022, was recorded in Debt, non-current on the balance sheets.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Cash and cash equivalents consisted of the following (in thousands): September 30, 2022 December 31, 2021 Cash $ 6,952 $ 17,065 Cash equivalents 52,658 152,974 Total cash and cash equivalents $ 59,610 $ 170,039 The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets to the total of such amounts shown on the statements of cash flows. The restricted cash is primarily collateral for performance bonds issued to certain customers. The collateral is provided in the form of a cash deposit to either support the bond directly or to collateralize a letter of credit that supports the performance bonds. September 30, 2022 December 31, 2021 Cash and cash equivalents $ 59,610 $ 170,039 Restricted cash, current portion 12,105 12,105 Restricted cash, net of current portion 460 460 Total restricted cash 12,565 12,565 Total cash and cash equivalents, and restricted cash $ 72,175 $ 182,604 Inventories consisted of the following (in thousands): September 30, 2022 December 31, 2021 Raw materials $ 110,185 $ 65,225 Work in progress 29,470 25,062 Finished goods 18,044 18,269 Service parts 7,135 6,000 Total inventories $ 164,834 $ 114,556 The write-down of excess or obsolete inventories to cost of goods sold was immaterial for the three and nine months ended September 30, 2022, and $0.6 million and $1.3 million for the three and nine months ended September 30, 2021, respectively. Property, plant, and equipment, net, consisted of the following (in thousands): September 30, 2022 December 31, 2021 Computer hardware $ 5,273 $ 5,195 Computer software 9,753 9,561 Internally used vehicles and charging systems 14,761 16,459 Leased vehicles and batteries 5,142 6,863 Leasehold improvements 10,679 10,516 Machinery and equipment 28,575 28,302 Office furniture and equipment 1,942 1,861 Tooling 21,859 21,726 Finance lease right-of-use assets 179 179 Construction in progress 59,174 20,243 157,337 120,905 Less: Accumulated depreciation and amortization (63,681) (58,659) Total $ 93,656 $ 62,246 Construction in progress was comprised of various assets that are not available for their intended use as of the balance sheet date, and mainly related to the equipment and facility build out at the battery manufacturing facility (Powered 1) in Greer, South Carolina. For the three and nine months ended September 30, 2022, depreciation and amortization expense were $2.9 million and $9.6 million, respectively. For the three and nine months ended September 30, 2021, depreciation and amortization expense were $3.9 million and $11.7 million, respectively. Accrued liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Accrued payroll and related expenses $ 10,821 $ 8,069 Accrued sales and use tax 1,102 885 Warranty reserve 8,413 8,116 Other accrued expenses 5,583 3,564 Total $ 25,919 $ 20,634 Other long-term liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Warranty reserve $ 16,630 $ 15,158 Finance lease liabilities, non-current 65 87 Total $ 16,695 $ 15,245

Debt

Debt	9 Months Ended
	Sep. 30, 2022
Debt Disclosure [Abstract]
Debt	Debt Debt, net of debt discount and issuance costs, consisted of the following (in thousands): September 30, 2022 December 31, 2021 PPP loan $ — $ 10,000 Convertible Notes 116,995 100,999 Total debt 116,995 110,999 Less debt, current — — Debt, non-current $ 116,995 $ 110,999 Senior Credit Facility In May 2019, the Company entered into a Loan, Guaranty and Security Agreement for a senior secured asset-based lending facility (the “Senior Credit Facility”) with borrowing capacity up to $75.0 million. The commitment under the Senior Credit Facility is available to the Company on a revolving basis through the earlier of May 2024 or 91 days prior to the stated maturity of any subordinated debt in aggregate amount of $7.5 million or more. The maximum availability under the Senior Credit Facility is based on eligible accounts receivable and inventory, subject to certain reserves, to be determined in accordance with the Senior Credit Facility. The commitment under the Senior Credit Facility includes a $20.0 million letter of credit sub-line as of September 30, 2022. Subject to certain conditions, the commitment may be increased by $50.0 million upon approval by the lender, and at the Company’s option, the commitment can be reduced to $25.0 million or terminated upon at least 15 days’ written notice. The Senior Credit Facility is secured by a security interest in substantially all of the Company’s assets except for intellectual property and other restricted property. Borrowings under the Senior Credit Facility bear interest at per annum rates equal to, at the Company’s option, either (i) the base rate plus an applicable margin for base rate loan, or (ii) the London Interbank Offered Rate (“LIBOR”) plus an applicable margin for LIBOR loan. The base rate is calculated as the greater of (a) the Lender prime rate, (b) the federal funds rate plus 0.5%, and (c) one-month LIBOR plus 1.0%. The applicable margin is calculated based on a pricing grid linked to quarterly average excess availability (as a percentage of borrowing capacity). For base rate loans, the applicable margin ranges from 0.0% to 1.5%, and for LIBOR loans, it ranges from 1.5% to 3.0%. The Senior Credit Facility contains certain customary non-financial covenants. In addition, the Senior Credit Facility requires the Company to maintain a fixed charge coverage ratio of at least 1.00:1.00 during such times as a covenant trigger event shall exist. There was no outstanding balance for borrowings under this Senior Credit Facility as of September 30, 2022 and December 31, 2021. There was an aggregate of $15.9 million in letters of credit outstanding as of September 30, 2022. Small Business Administration Loan In May 2020, the Company received Small Business Administration (the “SBA”) loan proceeds of $10.0 million from Town Center Bank pursuant to the Paycheck Protection Program (“the PPP loan”) under the “Coronavirus Aid, Relief and Economic Security (CARES) Act”. The PPP loan was in the form of a note with an original maturity in May 2022, and was extended to May 2025 based on the SBA’s interim final rule. The interest rate was 1.0% per annum. In May 2022, the SBA approved the Company’s PPP loan forgiveness application, and the PPP loan of $10.0 million was forgiven in full and the previously paid interest of approximately $0.2 million was refunded. A total of $10.2 million was recorded as gain on debt extinguishment in the Company’s consolidated statements of operations. Convertible Notes In August 2020, the Company entered into a Note Purchase Agreement for Secured Convertible Promissory Notes (the “Convertible Notes”). The Convertible Notes had an aggregate principal amount of $200.0 million, with cash interest of 5.0% per annum payable at each quarter end and a paid-in-kind interest of 4.5% per annum payable by increasing the principal balance at each quarter end. The Convertible Notes will mature in August 2025, and the Company may not make prepayment unless approved by the required holders of the Convertible Notes. Each of the Convertible Notes shall rank equally without preference or priority of any kind over one another, but senior in all rights, privileges and preferences to all other shares of the Company’s capital stock and all other securities of the Company that are convertible into or exercisable for the Company’s capital stock directly or indirectly. Prior to the maturity date or prior to the payment or conversion of the entire balance of the Convertible Notes, in the event of a liquidation or sale of the Company, the Company shall pay to the holders of Convertible Notes the greater of (i) 150% of the principal balance of the Convertible Notes or (ii) the consideration that the holders would have received had the holders elected to convert the Convertible Notes into common stock immediately prior to such liquidation event. The Convertible Notes do not entitle the holders to any voting rights or other rights as a stockholder of the Company, unless and until the Convertible Notes are actually converted into shares of the Company’s capital stock in accordance with their terms. The Note Purchase Agreement contains certain customary non-financial covenants. In addition, the Note Purchase Agreement requires the Company to maintain liquidity at quarter end of not less than the greater of (i) $75.0 million and (ii) four times of cash burn for the three-month period then ended. The Convertible Notes will mature in August 2025 or will be settled by issuing common stock, and accordingly are classified as a non-current liability on the Company’s balance sheets. In connection with the issuance of the Convertible Notes, the Company issued warrants to the holders of Convertible Notes to purchase 4.6 million shares of Company stock at an exercise price of $0.02 per share. The warrants are freestanding financial instruments and, prior to the Closing, were classified as a liability due to the possibility that they could become exercisable into Legacy Proterra convertible preferred stock. Upon the consummation of the Merger, the stock issuable upon exercise of the warrants is Proterra common stock, with no possibility to convert to Legacy Proterra convertible preferred stock. As a result, the carrying amount of the warrant liability was reclassified to stockholders’ equity. The warrant liability of $29.0 million was initially measured at fair value on its issuance date and recorded as a debt discount and amortized during the term of the Convertible Notes to interest expense using the effective-interest method. The warrant liability was remeasured on a recurring basis at each reporting period date, with the change in fair value reported in the statement of operations. Upon any exercise of the warrants to common stock, the carrying amount of the warrant liability is reclassified to stockholders’ equity. Prior to the Closing, the embedded features of the Convertible Notes were composed of conversion options that had the economic characteristics of a contingent early redemption feature settled in a variable number of shares of Company stock. These conversion options were bifurcated and accounted for separately from the host debt instrument. The derivative liability of $68.5 million was initially measured at fair value on the issuance date of the Convertible Notes and recorded as a debt discount and was amortized during the term of the Convertible Notes to interest expense using the effective-interest method. The derivative liability was remeasured on a recurring basis at each reporting period date, with the change in fair value reported in the statement of operations. Upon the consummation of the Merger, the embedded conversion features associated with the Convertible Notes no longer qualify for derivative accounting since the conversion price became fixed. The carrying amount of the embedded derivative, the fair value as of the Closing Date, was reclassified to stockholders’ equity in accordance with Topic 815, Derivatives and Hedging. Issuance costs of $5.1 million were also recorded as debt discount and are amortized during the term of the Convertible Notes to interest expense using the effective interest method. On June 14, 2021, certain Convertible Note holders with an original aggregate principal amount of $46.5 million elected to convert their Convertible Notes at the Closing. An aggregate of $48.8 million principal and interest was reclassified to additional paid-in capital, and $21.0 million of remaining related debt issuance costs were expensed to interest expense. The outstanding Convertible Notes including accrued interest will be automatically converted to common stock at $6.5712 per share pursuant to the mandatory conversion provisions, if and when the VWAP exceeds $9.86 over 20 consecutive days subsequent to January 13, 2022. The amortization expense of debt discount and issuance costs were $3.6 million and $10.4 million for the three and nine months ended September 30, 2022, respectively. The amortization expense of debt discount and issuance costs were $3.2 million and $31.5 million for the three and nine months ended September 30, 2021, respectively. The Convertible Notes, net of debt discount and issuance costs, consisted of the following (in thousands): September 30, 2022 December 31, 2021 Principal $ 153,500 $ 153,500 PIK interest 15,385 9,826 Total principal 168,885 163,326 Less debt discount and issuance costs (51,890) (62,327) Total Convertible Notes $ 116,995 $ 100,999 As of September 30, 2022, the contractual future principal repayments of the total debt were as follows (in thousands): 2022 $ — 2025 (1) 168,885 Total debt $ 168,885 __________________

Leases

Leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Leases	Leases As a Lessor The net investment in leases were as follows (in thousands): September 30, 2022 December 31, 2021 Net investment in leases, current $ 658 $ 411 Net investment in leases, non-current 8,722 5,179 Total net investment in leases $ 9,380 $ 5,590 Interest income from accretion of net investment in lease was not material in the three and nine months ended September 30, 2022 or 2021. Future minimum payments receivable from operating and sales-type leases as of September 30, 2022 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2022 $ 175 $ 145 2023 384 749 2024 — 1,010 2025 — 1,528 2026 — 1,528 Thereafter — 5,541 Total minimum lease payments $ 559 $ 10,501 As a Lessee The Company leases its office and manufacturing related facilities in Burlingame and City of Industry, California, Greenville and Greer, South Carolina, and Rochester Hills, Michigan under operating lease agreements with various expiration dates from 2023 through 2033. The Company had no material capital leases as of September 30, 2022. Maturities of operating lease liabilities as of September 30, 2022 were as follows (in thousands): Remainder of 2022 $ 2,065 2023 6,893 2024 4,224 2025 3,487 2026 2,615 Thereafter 12,096 Total undiscounted lease payment 31,380 Less: imputed interest (6,034) Total operating lease liabilities $ 25,346 Operating lease expense was $1.9 million and $5.4 million for the three and nine months ended September 30, 2022, respectively. Operating lease expense was $1.0 million and $3.0 million for the three and nine months ended September 30, 2021, respectively. Short-term and variable lease expenses for the nine months ended September 30, 2022 and 2021 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Nine Months Ended September 30, 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (4,822) $ (3,050) Operating lease right-of-use assets and liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Operating leases Operating lease right-of-use assets $ 24,169 $ 24,282 Operating lease liabilities, current 6,354 4,084 Operating lease liabilities, non-current 18,992 20,963 Total operating lease liabilities $ 25,346 $ 25,047 The weighted average remaining lease term and discount rate of operating leases were 6.6 years and 5.7%, respectively, as of September 30, 2022. The weighted average remaining lease term and discount rate of operating leases were 7.6 years and 5.8%, respectively, as of December 31, 2021. As of September 30, 2022, the Company had no significant additional operating leases and finance leases that have not yet commenced.
Leases	Leases As a Lessor The net investment in leases were as follows (in thousands): September 30, 2022 December 31, 2021 Net investment in leases, current $ 658 $ 411 Net investment in leases, non-current 8,722 5,179 Total net investment in leases $ 9,380 $ 5,590 Interest income from accretion of net investment in lease was not material in the three and nine months ended September 30, 2022 or 2021. Future minimum payments receivable from operating and sales-type leases as of September 30, 2022 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2022 $ 175 $ 145 2023 384 749 2024 — 1,010 2025 — 1,528 2026 — 1,528 Thereafter — 5,541 Total minimum lease payments $ 559 $ 10,501 As a Lessee The Company leases its office and manufacturing related facilities in Burlingame and City of Industry, California, Greenville and Greer, South Carolina, and Rochester Hills, Michigan under operating lease agreements with various expiration dates from 2023 through 2033. The Company had no material capital leases as of September 30, 2022. Maturities of operating lease liabilities as of September 30, 2022 were as follows (in thousands): Remainder of 2022 $ 2,065 2023 6,893 2024 4,224 2025 3,487 2026 2,615 Thereafter 12,096 Total undiscounted lease payment 31,380 Less: imputed interest (6,034) Total operating lease liabilities $ 25,346 Operating lease expense was $1.9 million and $5.4 million for the three and nine months ended September 30, 2022, respectively. Operating lease expense was $1.0 million and $3.0 million for the three and nine months ended September 30, 2021, respectively. Short-term and variable lease expenses for the nine months ended September 30, 2022 and 2021 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Nine Months Ended September 30, 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (4,822) $ (3,050) Operating lease right-of-use assets and liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Operating leases Operating lease right-of-use assets $ 24,169 $ 24,282 Operating lease liabilities, current 6,354 4,084 Operating lease liabilities, non-current 18,992 20,963 Total operating lease liabilities $ 25,346 $ 25,047 The weighted average remaining lease term and discount rate of operating leases were 6.6 years and 5.7%, respectively, as of September 30, 2022. The weighted average remaining lease term and discount rate of operating leases were 7.6 years and 5.8%, respectively, as of December 31, 2021. As of September 30, 2022, the Company had no significant additional operating leases and finance leases that have not yet commenced.
Leases	Leases As a Lessor The net investment in leases were as follows (in thousands): September 30, 2022 December 31, 2021 Net investment in leases, current $ 658 $ 411 Net investment in leases, non-current 8,722 5,179 Total net investment in leases $ 9,380 $ 5,590 Interest income from accretion of net investment in lease was not material in the three and nine months ended September 30, 2022 or 2021. Future minimum payments receivable from operating and sales-type leases as of September 30, 2022 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2022 $ 175 $ 145 2023 384 749 2024 — 1,010 2025 — 1,528 2026 — 1,528 Thereafter — 5,541 Total minimum lease payments $ 559 $ 10,501 As a Lessee The Company leases its office and manufacturing related facilities in Burlingame and City of Industry, California, Greenville and Greer, South Carolina, and Rochester Hills, Michigan under operating lease agreements with various expiration dates from 2023 through 2033. The Company had no material capital leases as of September 30, 2022. Maturities of operating lease liabilities as of September 30, 2022 were as follows (in thousands): Remainder of 2022 $ 2,065 2023 6,893 2024 4,224 2025 3,487 2026 2,615 Thereafter 12,096 Total undiscounted lease payment 31,380 Less: imputed interest (6,034) Total operating lease liabilities $ 25,346 Operating lease expense was $1.9 million and $5.4 million for the three and nine months ended September 30, 2022, respectively. Operating lease expense was $1.0 million and $3.0 million for the three and nine months ended September 30, 2021, respectively. Short-term and variable lease expenses for the nine months ended September 30, 2022 and 2021 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Nine Months Ended September 30, 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (4,822) $ (3,050) Operating lease right-of-use assets and liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Operating leases Operating lease right-of-use assets $ 24,169 $ 24,282 Operating lease liabilities, current 6,354 4,084 Operating lease liabilities, non-current 18,992 20,963 Total operating lease liabilities $ 25,346 $ 25,047 The weighted average remaining lease term and discount rate of operating leases were 6.6 years and 5.7%, respectively, as of September 30, 2022. The weighted average remaining lease term and discount rate of operating leases were 7.6 years and 5.8%, respectively, as of December 31, 2021. As of September 30, 2022, the Company had no significant additional operating leases and finance leases that have not yet commenced.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments As of September 30, 2022, the Company had outstanding inventory and other purchase commitments of $2.3 billion. Most of the commitments relate to the expected purchase of cylindrical cells manufactured at a yet to be built LG Energy Solution battery cell plant in the United States, pursuant to a long-term supply agreement through 2028. The terms of the agreement require the Company to make certain prepayments that vary in size and that are made as milestones are met on the construction of the US facility. As of September 30, 2022, the Company has made a $10.0 million prepayment, which was recorded as the long-term inventory prepayment on the consolidated balance sheets. We expect our next prepayment to be made within the next six to twelve months. The prepayments will be recouped by the Company by offsetting a predetermined amount per unit on cells purchased from LG Energy Solution. Letters of Credit As of September 30, 2022, the Company had letters of credit outstanding totaling $16.1 million. Legal Proceedings The Company accrues contingent liabilities when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. From time to time in the normal course of business, various claims and litigation have been asserted or commenced. Due to uncertainties inherent in litigation and other claims, the Company can give no assurance that it will prevail in any such matters, which could subject the Company to significant liability or damages. Any claims or litigation could have an adverse effect on the Company’s business, financial position, operating results, or cash flows in or following the period that claims or litigation are resolved.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity On June 14, 2021, the Merger was consummated and, following the Closing, the Company is authorized to issue 510,000,000 shares of capital stock, with a par value of $0.0001 per share. The authorized shares consist of 500,000,000 shares of common stock and 10,000,000 shares of preferred stock. As of September 30, 2022, 225,532,429 shares of common stock were issued and outstanding, and no shares of preferred stock were issued and outstanding. The holders of each share of common stock are entitled to one vote per share. The Company has retroactively adjusted the shares of Legacy Proterra stock issued and outstanding prior to June 14, 2021 to give effect to the Exchange Ratio of 0.8925 established in the Merger Agreement to determine the number of shares of Proterra common stock into which they were converted. Immediately prior to the Merger, Legacy Proterra was authorized to issue 271,920,636 shares of stock, with a par value of $0.0001 per share, with 156,276,750 shares designated as common stock and 115,643,886 shares of convertible preferred stock. All of the outstanding Legacy Proterra convertible preferred stock was converted to Legacy Proterra common stock immediately prior to the Merger. See Note 3, Reverse Recapitalization. As of September 30, 2022, the Company had reserved shares of common stock for issuance as follows (in thousands): 2010 Equity Incentive Plan 17,072 2021 Equity Incentive Plan 20,455 2021 Employee Stock Purchase Plan 3,524 Warrants 1 Earnout Stock 18,009 Convertible notes 26,316 Total 85,377

Equity Plans and Stock-based Co

Equity Plans and Stock-based Compensation	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Equity Plans and Stock-based Compensation	Equity Plans and Stock-based Compensation 2010 Equity Incentive Plan In 2010, Legacy Proterra adopted the 2010 Equity Incentive Plan (the “2010 Plan”), which provided for the grant of stock options, stock appreciation rights, restricted stock, and restricted stock units. Upon Closing, the then outstanding options under the 2010 Plan were converted into options exercisable to purchase an aggregate of 22,532,619 shares of common stock. Following the Closing, such options continue to be subject to the terms of the 2010 Plan and applicable award agreements; however, no further awards can be granted under the 2010 Plan. As of September 30, 2022, options to purchase 17,072,030 shares of common stock remained outstanding under the 2010 Plan. 2021 Equity Incentive Plan The 2021 Plan was adopted by the ArcLight Board prior to the Closing, approved by ArcLight’s shareholders on June 11, 2021, and became effective upon the Closing Date. The Equity Incentive Plan allows the Company to grant awards of stock options, restricted stock awards, stock appreciation rights, restricted stock units (“RSUs”), performance awards, and stock bonus awards to officers, employees, directors and consultants. The Company initially reserved 10,000,000 shares of common stock, plus 387,531 reserved shares not issued under the 2010 Plan on the effective date of the 2021 Plan. The number of shares reserved for issuance under the 2021 Plan increases automatically on January 1 of each of 2022 through 2031 by the number of shares equal to the lesser of 4% of the total number of outstanding shares of all classes of common stock as of the immediately preceding December 31, or a number as may be determined by the Board. In the first quarter of 2022, the shares reserved for issuance were increased by 8,878,388 additional shares. Stock option and RSU awards generally vest annually over a four-year period. 2021 Employee Stock Purchase Plan Proterra’s 2021 Employee Stock Purchase Plan (the “ESPP”), including the authorization of the initial share reserve thereunder, was adopted by the ArcLight Board prior to the Closing, approved by ArcLight’s shareholders on June 11, 2021, and became effective upon the Closing Date. An aggregate of 1,630,000 shares of common stock were reserved and available for sale under the ESPP. The aggregate number of shares reserved for sale under the ESPP increases automatically on January 1 of each of 2022 through 2031 by a number of shares equal to the lesser of 1% of the total number of outstanding shares of common stock as of the immediately preceding December 31 or a number of shares as may be determined by the Board or the compensation committee. The aggregate number of shares issued over the term of the ESPP, subject to certain adjustments, may not exceed 16,300,000 shares. In the first quarter of 2022, the shares reserved for issuance were increased by 2,219,597 additional shares. The ESPP allows eligible employees to purchase shares of common stock at a discount through payroll deductions of up to 15% of their eligible compensation, at not less than 85% of the fair market value, as defined in the ESPP, subject to any plan limitations. A participant may purchase a maximum of 2,500 shares during each 6-month offering period and $25,000 in any one calendar year. The offering periods generally start on the first trading day on or after November 15th and May 15th of each year. The first offering period started in the fourth quarter of 2021. The Company calculated the fair value of the employees’ purchase rights relating to the ESPP using the Black-Scholes model and recorded approximately $1.0 million of stock-based compensation expense for the nine months ended September 30, 2022. In the nine months ended September 30, 2022, the Company issued 325,106 shares of common stock under the ESPP with a purchase price of $4.62 per share. A summary of the Company’s stock option activity and related information was as follows: Options Outstanding Number of Stock Options Outstanding Weighted- Average Exercise Price Weighted-Average Remaining Contractual Life Aggregate Intrinsic Value Balance as of December 31, 2021 (1) 18,101,584 4.08 5.5 $ 87,425 Granted 758,528 7.70 Exercised (2,912,066) 3.04 Cancelled/forfeited/expired (1,262,183) 6.10 Balance as of September 30, 2022 (1) 14,685,863 4.30 5.7 $ 17,159 Exercisable as of September 30, 2022 (2) 11,757,906 3.80 5.0 $ 16,790 __________________ (1) Excluding Equity Awards of 2,677,500 shares and Milestone Options of 669,375 shares. See below for further details. (2) Excluding 1,673,436 shares exercisable under the Equity Awards with weighted average exercise price of $19.61 per share as of September 30, 2022. In March 2020, in conjunction with Mr. Allen’s appointment as the then President and Chief Executive Officer, the board of directors of Legacy Proterra approved a grant to Mr. Allen of stock option awards with respect to 4,685,624 shares, comprised of (1) 1,338,749 shares of a time-based award with an exercise price of $5.33 per share vesting quarterly over four years, (2) 2,677,500 shares of a time-based award consisting of four tranches with an exercise price of $11.21, $16.81, $22.41 and $28.02 per share, respectively, and vesting quarterly over four years (“Equity Awards”), and (3) 669,375 shares of milestone-based award with an exercise price of $5.33 per share vesting entirely and becoming exercisable on the first trading day following the expiration of the lockup period of the Company’s initial public offering or the consummation of a change in control of the Company or upon the consummation of a merger involving a special purpose acquisition company (“Milestone Options”). The stock-based compensation expense for Milestone Options was recognized at the time the performance milestone became probable of achievement, which was at the time of Closing. Upon Closing, the 669,375 shares underlying the Milestone Options fully vested, and $2.1 million stock-based compensation expense was recognized in June 2021. Aggregate intrinsic value represents the difference between the estimated fair value of the underlying common stock and the exercise price of outstanding, in-the-money stock options. The total intrinsic value of stock options exercised was $10.0 million for the nine months ended September 30, 2022. The total estimated grant date fair value of stock options vested was $7.4 million for the nine months ended September 30, 2022. As of September 30, 2022, the total unrecognized stock-based compensation expense related to outstanding stock options was $15.2 million, which is expected to be recognized over a weighted-average period of 2.0 years. The fair value of stock options granted is estimated on the date of grant using the following assumptions: Nine Months Ended September 30, 2022 2021 Expected term (in years) 6.3 6.2 Risk-free interest rate 2.0 % 1.0 % Expected volatility 55.1 % 53.9 % Expected dividend rate — — Restricted Stock Units A summary of the Company's RSU activity and related information is as follows: Number of RSUs Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Balance as of December 31, 2021 1,324,960 $ 10.67 $ 11,699 Granted 4,589,454 6.91 Released (335,546) 10.25 Forfeited (514,260) 8.96 Balance as of September 30, 2022 5,064,608 $ 7.46 $ 25,222 The Company started granting RSUs to employees in the third quarter of 2021. As of September 30, 2022, the total unrecognized stock-based compensation expense related to outstanding RSUs was $33.0 million, which is expected to be recognized over a weighted-average period of 3.2 years. Stock-based Compensation Expense Stock-based compensation expense included in operating results was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Cost of goods sold $ 456 $ 319 $ 1,350 $ 865 Research and development 1,409 567 3,690 1,625 Selling, general and administrative 3,491 2,292 11,273 8,775 Total stock-based compensation expense $ 5,356 $ 3,178 $ 16,313 $ 11,265

Net Income (Loss) Per Share

Net Income (Loss) Per Share	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	Net Income (Loss) Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less the weighted-average unvested common stock subject to repurchase or forfeiture as they are not deemed to be issued for accounting purposes. Diluted net loss per share is computed by giving effect to all potential shares of common stock, including stock options, RSUs and warrants, to the extent they are dilutive. The computation of basic and diluted net income (loss) per share of common stock attributable to common stockholders was as follows (in thousands, except for per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Numerator: Net income (loss) $ (65,061) $ 36,321 $ (156,960) $ (204,868) Effect of dilutive securities: Gain on valuation of warrant liabilities — (73,197) — — Interest expense to be recognized upon conversion of Convertible Notes (1) (47,891) (61,774) (40,154) — Numerator for diluted EPS - Net loss after the effect of dilutive securities $ (112,952) $ (98,650) $ (197,114) $ (204,868) Denominator: Weighted-average shares used in computing net loss per share of common stock, basic 225,291 212,071 223,782 89,233 Dilutive impact of public and private placement warrants — 594 — — Convertible Notes (1) 25,413 24,300 24,855 — Diluted weighted average shares 250,704 236,965 248,637 89,233 Net income (loss) per share of common stock: Basic $ (0.29) $ 0.17 $ (0.70) $ (2.30) Diluted $ (0.45) $ (0.42) $ (0.79) $ (2.30) __________________ (1) Adjustment is under the “if-converted” method. Adjustment for the three months ended September 30, 2022 includes write-off of $55.5 million unamortized debt discount of the Convertible Notes as of September 30, 2022, offset by the $7.6 million interest expense recorded in net loss of three months ended September 30, 2022. Adjustment for the nine months ended September 30, 2022 includes write-off of $62.3 million unamortized debt discount of the Convertible Notes as of December 31, 2021, offset by the $22.2 million interest expense recorded in net loss of nine months ended September 30, 2022. As a result of the Merger, the Company has retroactively adjusted the weighted-average number of shares of common stock outstanding prior to the Closing Date by multiplying them by the Exchange Ratio of 0.8925 used to determine the number of shares of common stock into which they converted. Prior to the Closing Date, the Company applied the two-class method to calculate its basic and diluted net loss per share of common stock, as the convertible preferred stock were participating securities. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common stockholders. However, the two-class method did not impact the net loss per share of common stock as the Company was in a loss position and holders of convertible preferred stock did not participate in losses. Following the Closing Date, the Company applies the treasury stock method when calculating the diluted net income (loss) per share of common stock and “if-converted” method for Convertible Notes when applicable. The outstanding Convertible Notes including accrued interest will be automatically converted to common stock at $6.5712 per share pursuant to the mandatory conversion provisions, if and when the VWAP exceeds $9.86 over 20 consecutive days subsequent to January 13, 2022. Since the Company was in a loss position after the effect of dilutive securities, no adjustment is required to the weighted-average shares used in computing the diluted net loss per share as the inclusion of the remaining potential common stock shares outstanding would have been anti-dilutive. The potentially dilutive securities were as follows (in thousands): September 30, 2022 Stock options and RSUs to purchase common stock 23,097 Warrants to purchase common stock 1 23,098

401(k) Plan

401(k) Plan	9 Months Ended
	Sep. 30, 2022
Retirement Benefits [Abstract]
401(k) Plan	401(k) Plan The Company sponsors a 401(k) defined contribution plan covering all eligible employees and provides a matching contribution for the first 4% of their salaries. The matching contribution costs incurred were $0.9 million and $2.4 million in the three and nine months ended September 30, 2022, respectively. The matching contribution costs incurred were $0.6 million and $1.8 million in the three and nine months ended September 30, 2021, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”). The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation. Certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2021 and the related notes incorporated by referenced in the Company’s Annual Report (the “Annual Report”) on Form 10-K, filed with SEC on March 14, 2022, which provides a more complete discussion of the Company’s accounting policies and certain other information. The information as of December 31, 2021 and 2020 was derived from the Company’s audited financial statements. The condensed consolidated financial statements were prepared on the same basis as the audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for a fair presentation of the Company’s financial position as of September 30, 2022 and the results of operations and cash flows for the three and nine months ended September 30, 2022 and 2021. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results that may be expected for the year ending December 31, 2022.
Use of Estimates	Use of Estimates In preparing the condensed consolidated financial statements and related disclosures in conformity with U.S. GAAP and pursuant to the rules and regulations of the SEC, the Company must make estimates and judgments that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results may differ materially from these estimates.
Segments	SegmentsThe Company operates in the United States and has sales to the European Union, Canada, United Kingdom, Australia, Japan and Turkey.The Company’s chief operating decision maker is its Chief Executive Officer, who reviews financial information presented at the entity level. Accordingly, the Company has determined that it has a single reportable segment.
Accounts Receivable and Allowance for Credit Losses	Accounts Receivable and Allowance for Credit Losses Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company determines the allowance for credit losses based on historical write-off experience, an analysis of the aging of outstanding receivables, customer payment patterns and expectations of changes in macroeconomic conditions that may affect the collectability of outstanding receivables. The allowance for credit losses was not material as of September 30, 2022 and December 31, 2021.
Credit Risk and Concentration	Credit Risk and Concentration The Company’s financial instruments that are potentially subject to concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, short-term investments, and accounts receivable. Cash and cash equivalents and short-term investments are maintained primarily at one financial institution as of September 30, 2022, and deposits exceed federally insured limits. Risks associated with cash and cash equivalents, and short-term investments are mitigated by banking with creditworthy financial institutions. The Company has not experienced any losses on its deposits of cash and cash equivalents or its short-term investments. Cash equivalents and short-term investments consist of short-term money market funds, corporate debt securities, and debt securities issued by the U.S. Treasury, which are deposited with reputable financial institutions. The Company’s cash management and investment policy limits investment instruments to securities with short-term credit ratings at the timing of purchase of P-2 and A-2 or better from Moody’s Investors Service and Standard & Poor’s Financial Services, LLC, respectively, with the objective to preserve capital and to maintain liquidity until the funds can be used in business operations. Accounts receivable are typically unsecured and are generally derived from revenue earned from transit agencies, universities and airports in North America and global commercial vehicle manufacturers in North America, the European Union, the United Kingdom, Australia, Japan and Turkey. The Company periodically evaluates the collectability of its accounts receivable and provides an allowance for potential credit losses as necessary. Given the large order value for customers and the relatively low number of customers, revenue and accounts receivable have typically been concentrated with a limited number of customers. Revenue Accounts Receivable Three Months Ended September 30, Nine Months Ended September 30, September 30, December 31, 2022 2021 2022 2021 2022 2021 Number of customers accounted for 10% or more 2 2 2 — 2 1 Total % for customers accounted for 10% or more 40 % 30 % 27 % — % 40 % 18 % Single source suppliers provide the Company with a number of components that are required for manufacturing of its current products. In other instances, although there may be multiple suppliers available, many of the components are purchased from one single source. If these single source suppliers fail to meet the Company’s requirements on a timely basis at competitive prices or are unable to provide components for any reason, the Company could suffer manufacturing delays, a possible loss of revenue, or incur higher cost of sales, any of which could adversely impact the Company’s operating results.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates the recoverability of property, plant, and equipment and right-of-use assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review indicates that the carrying amount of long-lived assets is not recoverable, the carrying amount of such assets is reduced to fair value. In addition to the recoverability assessment, the Company periodically reviews the remaining estimated useful lives of property, plant, and equipment. If the estimated useful life assumption for any asset is reduced, the remaining net book value is depreciated over the revised estimated useful life.
Deferred Revenue and Revenue Recognition	Deferred Revenue Deferred revenue consists of billings or payments received in advance of revenue recognition that are recognized as revenue once the revenue recognition criteria are met. In some instances, progress billings are issued upon meeting certain milestones stated in the contracts. Accordingly, the deferred revenue balance does not represent the total contract value of non-cancelable arrangements. Invoices are typically due within 30 to 40 days. The changes in deferred revenue consisted of the following (in thousands): Deferred revenue as of December 31, 2021 $ 36,406 Revenue recognized from beginning balance during the nine months ended September 30, 2022 (10,972) Deferred revenue added during the nine months ended September 30, 2022 16,073 Deferred revenue as of September 30, 2022 $ 41,507 The current portion of deferred revenue represents the amount that is expected to be recognized as revenue within one year from the balance sheet date. Revenue Recognition The Company derives revenue primarily from the sale of vehicles and charging systems, the installation of charging systems, the sale of battery systems and powertrain components to other vehicle manufacturers, as well as the sale of spare parts and other services provided to customers. Product revenue consists of revenue earned from vehicles and charging systems, battery systems and powertrain components, installation of charging systems, and revenue from leased vehicles, charging systems, and batteries under operating leases. Leasing revenue recognized over time was approximately $0.2 million and $0.5 million in the three months ended September 30, 2022 and 2021, respectively, and $0.9 million and $1.6 million in the nine months ended September 30, 2022 and 2021, respectively. Parts and other service revenue includes revenue earned from spare parts, the design and development of battery systems and powertrain systems for other vehicle manufacturers, and extended warranties. The Company recognizes revenue when or as it satisfies a performance obligation by transferring control of a product or service to a customer. Revenue from product sales is recognized when control of the underlying performance obligations is transferred to the customer. Revenue from sales of vehicles is typically recognized upon delivery when the Company can objectively demonstrate that the criteria specified in the contractual acceptance provisions are achieved prior to delivery. In cases, where the Company cannot objectively demonstrate that the criteria specified in the contractual acceptance provisions have been achieved prior to delivery, revenue is recognized upon acceptance by the customer. Revenue from sales of charging systems is recognized at a point in time, generally upon delivery or commissioning when control of the underlying performance obligations are transferred to the customer. Under certain contract arrangements, the control of the performance obligations related to the charging systems is transferred over time, and the associated revenue is recognized over the installation period using an input measure based on costs incurred to date relative to total estimated costs to completion. Spare parts revenue is recognized upon shipment. Extended warranty revenue is recognized over the life of the extended warranty using the time elapsed method. Development service contracts typically include the delivery of prototype products to customers. The performance obligation associated with the development of prototype products as well as battery systems and powertrain components to other vehicle manufacturers, is satisfied at a point in time, typically upon shipping. Revenue derived from performance obligations satisfied over time from charging systems and installation was $3.7 million and $0.2 million for the three months ended September 30, 2022 and 2021, respectively, and $5.8 million and $5.3 million for the nine months ended September 30, 2022 and 2021, respectively. Extended warranty revenue was $0.4 million and $0.6 million for the three months ended September 30, 2022 and 2021, respectively, and $1.5 million and $1.3 million for the nine months ended September 30, 2022 and 2021, respectively. As of September 30, 2022 and December 31, 2021, the contract assets balance was $10.2 million and $1.3 million, respectively. The contract assets are expected to be billed within the next twelve months and are recorded in prepaid expenses and other current assets on the Company’s balance sheets. As of September 30, 2022, the amount of remaining performance obligations that have not been recognized as revenue was $413.8 million, of which 85% were expected to be recognized as revenue over the next 12 months and the remainder thereafter. This amount excludes the value of remaining performance obligations for contracts with an original expected length of one year or less. Our business is organized into two business units with three business lines, each of which addresses a critical component of the commercial vehicle electrification value proposition in a complementary and self-reinforcing manner: • Proterra Transit designs, develops, manufactures, and sells electric transit buses as an original equipment manufacturer (“OEM”) for North American public transit agencies, airports, universities, and other commercial transit fleets. • Proterra Powered & Energy includes Proterra Powered, which designs, develops, manufactures, sells, and integrates proprietary battery systems and electrification solutions into vehicles for global commercial vehicle OEMs, and Proterra Energy, which provides turnkey fleet-scale, high-power charging solutions
Product Warranties	Product WarrantiesWarranty expense is recorded as a component of cost of goods sold.
Adoption of New Accounting Standards	ASU No. 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity . This standard simplifies the accounting for convertible instruments by removing certain separation models in ASC 470- 20, Debt—Debt with Conversion and Other Options . This standard updates the guidance on certain embedded conversion features that are not required to be accounted for as derivatives under Topic 815, Derivatives and Hedging , or that do not result in substantial premiums accounted for as paid-in capital, such that those features are no longer required to be separated from the host contract. The convertible debt instruments will be accounted for as a single liability measured at amortized cost. This will also result in the interest expense recognized for convertible debt instruments to be typically closer to the coupon interest rate when applying the guidance in Topic 835, Interest . Further, this standard made amendments to the EPS guidance in Topic 260 for convertible instruments, the most significant impact of which is requiring the use of the if-converted method for diluted earnings per share calculation, and no longer allowing the net share settlement method. This standard also made revisions to Topic 815-40, which provides guidance on how an entity must determine whether a contract qualifies for a scope exception from derivative accounting. The amendments to Topic 815-40 change the scope of contracts that are recognized as assets or liabilities. The Company adopted this standard on January 1, 2022, and it had no material impact on the condensed consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Revenue Disaggregated by Geography	Revenue disaggregated by geography, based on the addresses of the Company’s customers, consists of the following (in Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 United States $ 82,040 $ 59,482 $ 195,680 $ 163,972 Rest of World 14,183 2,459 33,688 10,477 96,223 61,941 $ 229,368 $ 174,449
Concentration of Customer Risk	Revenue Accounts Receivable Three Months Ended September 30, Nine Months Ended September 30, September 30, December 31, 2022 2021 2022 2021 2022 2021 Number of customers accounted for 10% or more 2 2 2 — 2 1 Total % for customers accounted for 10% or more 40 % 30 % 27 % — % 40 % 18 %
Deferred Revenue	The changes in deferred revenue consisted of the following (in thousands): Deferred revenue as of December 31, 2021 $ 36,406 Revenue recognized from beginning balance during the nine months ended September 30, 2022 (10,972) Deferred revenue added during the nine months ended September 30, 2022 16,073 Deferred revenue as of September 30, 2022 $ 41,507
Revenue of Business Units	The revenue of business units are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Proterra Transit $ 56,363 $ 50,175 $ 142,563 $ 140,187 Proterra Powered & Energy 39,860 11,766 86,805 34,262 Total $ 96,223 $ 61,941 $ 229,368 $ 174,449
Accrued Warranty Activity	Accrued warranty activity consisted of the following (in thousands): Nine Months Ended September 30, 2022 Warranty reserve - beginning of period $ 23,274 Warranty costs incurred (6,759) Net changes in liability for pre-existing warranties, including expirations (2,625) Provision for warranty 11,153 Warranty reserve - end of period $ 25,043

Reverse Recapitalization (Table

Reverse Recapitalization (Tables)	9 Months Ended
	Sep. 30, 2022
Reverse Recapitalization [Abstract]
Schedule Of Reverse Recapitalization	The number of shares of Proterra common stock issued immediately following the consummation of the Merger was (in thousands): Shares ArcLight Class A ordinary shares, outstanding prior to Merger 27,750 Less redemption of ArcLight shares (15) Sponsor 6,257 Sponsor Earnout Stock 680 Common stock of ArcLight 34,672 PIPE Investors 41,500 Legacy Proterra shares 131,176 Total shares of common stock immediately after Merger 207,348

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Financial Assets Measured at Fair Value on a Recurring Basis	Financial assets measured at fair value on a recurring basis using the above input categories were as follows (in thousands): Pricing Category Fair Value at September 30, 2022 December 31, 2021 Assets: Cash equivalents and marketable securities: Money market funds Level 1 $ 44,696 $ 102,978 U.S. Treasury securities Level 1 7,962 49,996 Short-term investments: U.S. Treasury securities Level 1 348,938 330,053 Corporate debt securities Level 2 — 160,914 Total $ 401,596 $ 643,941
Summary of Cash Equivalents and Marketable Securities	The following is a summary of cash equivalents and marketable securities as of September 30, 2022 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 44,696 $ — $ 44,696 U.S. Treasury securities 7,962 — 7,962 Short-term investments: U.S. Treasury securities 351,007 (2,069) 348,938 Total $ 403,665 $ (2,069) $ 401,596 The following is a summary of cash equivalents and marketable securities as of December 31, 2021 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 102,978 $ — $ 102,978 U.S. Treasury securities 49,996 — 49,996 Short-term investments: U.S. Treasury securities 330,618 (565) 330,053 Corporate debt securities 160,937 (23) 160,914 Total $ 644,529 $ (588) $ 643,941

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents	Cash and cash equivalents consisted of the following (in thousands): September 30, 2022 December 31, 2021 Cash $ 6,952 $ 17,065 Cash equivalents 52,658 152,974 Total cash and cash equivalents $ 59,610 $ 170,039 The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets to the total of such amounts shown on the statements of cash flows. The restricted cash is primarily collateral for performance bonds issued to certain customers. The collateral is provided in the form of a cash deposit to either support the bond directly or to collateralize a letter of credit that supports the performance bonds. September 30, 2022 December 31, 2021 Cash and cash equivalents $ 59,610 $ 170,039 Restricted cash, current portion 12,105 12,105 Restricted cash, net of current portion 460 460 Total restricted cash 12,565 12,565 Total cash and cash equivalents, and restricted cash $ 72,175 $ 182,604
Inventories	Inventories consisted of the following (in thousands): September 30, 2022 December 31, 2021 Raw materials $ 110,185 $ 65,225 Work in progress 29,470 25,062 Finished goods 18,044 18,269 Service parts 7,135 6,000 Total inventories $ 164,834 $ 114,556
Property, Plant and Equipment, Net	Property, plant, and equipment, net, consisted of the following (in thousands): September 30, 2022 December 31, 2021 Computer hardware $ 5,273 $ 5,195 Computer software 9,753 9,561 Internally used vehicles and charging systems 14,761 16,459 Leased vehicles and batteries 5,142 6,863 Leasehold improvements 10,679 10,516 Machinery and equipment 28,575 28,302 Office furniture and equipment 1,942 1,861 Tooling 21,859 21,726 Finance lease right-of-use assets 179 179 Construction in progress 59,174 20,243 157,337 120,905 Less: Accumulated depreciation and amortization (63,681) (58,659) Total $ 93,656 $ 62,246
Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Accrued payroll and related expenses $ 10,821 $ 8,069 Accrued sales and use tax 1,102 885 Warranty reserve 8,413 8,116 Other accrued expenses 5,583 3,564 Total $ 25,919 $ 20,634
Other Long-Term Liabilities	Other long-term liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Warranty reserve $ 16,630 $ 15,158 Finance lease liabilities, non-current 65 87 Total $ 16,695 $ 15,245

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2022
Debt Disclosure [Abstract]
Debt	Debt, net of debt discount and issuance costs, consisted of the following (in thousands): September 30, 2022 December 31, 2021 PPP loan $ — $ 10,000 Convertible Notes 116,995 100,999 Total debt 116,995 110,999 Less debt, current — — Debt, non-current $ 116,995 $ 110,999
Convertible Notes	The Convertible Notes, net of debt discount and issuance costs, consisted of the following (in thousands): September 30, 2022 December 31, 2021 Principal $ 153,500 $ 153,500 PIK interest 15,385 9,826 Total principal 168,885 163,326 Less debt discount and issuance costs (51,890) (62,327) Total Convertible Notes $ 116,995 $ 100,999
Contractual Future Principal Repayments of Debt	As of September 30, 2022, the contractual future principal repayments of the total debt were as follows (in thousands): 2022 $ — 2025 (1) 168,885 Total debt $ 168,885 __________________

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Net Investment in Leases	The net investment in leases were as follows (in thousands): September 30, 2022 December 31, 2021 Net investment in leases, current $ 658 $ 411 Net investment in leases, non-current 8,722 5,179 Total net investment in leases $ 9,380 $ 5,590
Future Minimum Payments Receivable from Operating Leases	Future minimum payments receivable from operating and sales-type leases as of September 30, 2022 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2022 $ 175 $ 145 2023 384 749 2024 — 1,010 2025 — 1,528 2026 — 1,528 Thereafter — 5,541 Total minimum lease payments $ 559 $ 10,501
Future Minimum Payments Receivable from Sales-Type Leases	Future minimum payments receivable from operating and sales-type leases as of September 30, 2022 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2022 $ 175 $ 145 2023 384 749 2024 — 1,010 2025 — 1,528 2026 — 1,528 Thereafter — 5,541 Total minimum lease payments $ 559 $ 10,501
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of September 30, 2022 were as follows (in thousands): Remainder of 2022 $ 2,065 2023 6,893 2024 4,224 2025 3,487 2026 2,615 Thereafter 12,096 Total undiscounted lease payment 31,380 Less: imputed interest (6,034) Total operating lease liabilities $ 25,346
Supplemental Cash Flow Information	Supplemental cash flow information related to leases were as follows (in thousands): Nine Months Ended September 30, 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (4,822) $ (3,050)
Operating Lease Right-Of-Use Assets and Liabilities	Operating lease right-of-use assets and liabilities consisted of the following (in thousands): September 30, 2022 December 31, 2021 Operating leases Operating lease right-of-use assets $ 24,169 $ 24,282 Operating lease liabilities, current 6,354 4,084 Operating lease liabilities, non-current 18,992 20,963 Total operating lease liabilities $ 25,346 $ 25,047

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Reserved Shares of Common Stock	As of September 30, 2022, the Company had reserved shares of common stock for issuance as follows (in thousands): 2010 Equity Incentive Plan 17,072 2021 Equity Incentive Plan 20,455 2021 Employee Stock Purchase Plan 3,524 Warrants 1 Earnout Stock 18,009 Convertible notes 26,316 Total 85,377

Equity Plans and Stock-based _2

Equity Plans and Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock Option Activity	A summary of the Company’s stock option activity and related information was as follows: Options Outstanding Number of Stock Options Outstanding Weighted- Average Exercise Price Weighted-Average Remaining Contractual Life Aggregate Intrinsic Value Balance as of December 31, 2021 (1) 18,101,584 4.08 5.5 $ 87,425 Granted 758,528 7.70 Exercised (2,912,066) 3.04 Cancelled/forfeited/expired (1,262,183) 6.10 Balance as of September 30, 2022 (1) 14,685,863 4.30 5.7 $ 17,159 Exercisable as of September 30, 2022 (2) 11,757,906 3.80 5.0 $ 16,790 __________________ (1) Excluding Equity Awards of 2,677,500 shares and Milestone Options of 669,375 shares. See below for further details. (2) Excluding 1,673,436 shares exercisable under the Equity Awards with weighted average exercise price of $19.61 per share as of September 30, 2022.
Assumptions for Fair Value of Stock Options	The fair value of stock options granted is estimated on the date of grant using the following assumptions: Nine Months Ended September 30, 2022 2021 Expected term (in years) 6.3 6.2 Risk-free interest rate 2.0 % 1.0 % Expected volatility 55.1 % 53.9 % Expected dividend rate — —
RSU Activity	A summary of the Company's RSU activity and related information is as follows: Number of RSUs Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Balance as of December 31, 2021 1,324,960 $ 10.67 $ 11,699 Granted 4,589,454 6.91 Released (335,546) 10.25 Forfeited (514,260) 8.96 Balance as of September 30, 2022 5,064,608 $ 7.46 $ 25,222
Stock-Based Compensation Expense	Stock-based compensation expense included in operating results was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Cost of goods sold $ 456 $ 319 $ 1,350 $ 865 Research and development 1,409 567 3,690 1,625 Selling, general and administrative 3,491 2,292 11,273 8,775 Total stock-based compensation expense $ 5,356 $ 3,178 $ 16,313 $ 11,265

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The computation of basic and diluted net income (loss) per share of common stock attributable to common stockholders was as follows (in thousands, except for per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Numerator: Net income (loss) $ (65,061) $ 36,321 $ (156,960) $ (204,868) Effect of dilutive securities: Gain on valuation of warrant liabilities — (73,197) — — Interest expense to be recognized upon conversion of Convertible Notes (1) (47,891) (61,774) (40,154) — Numerator for diluted EPS - Net loss after the effect of dilutive securities $ (112,952) $ (98,650) $ (197,114) $ (204,868) Denominator: Weighted-average shares used in computing net loss per share of common stock, basic 225,291 212,071 223,782 89,233 Dilutive impact of public and private placement warrants — 594 — — Convertible Notes (1) 25,413 24,300 24,855 — Diluted weighted average shares 250,704 236,965 248,637 89,233 Net income (loss) per share of common stock: Basic $ (0.29) $ 0.17 $ (0.70) $ (2.30) Diluted $ (0.45) $ (0.42) $ (0.79) $ (2.30) __________________ (1) Adjustment is under the “if-converted” method. Adjustment for the three months ended September 30, 2022 includes write-off of $55.5 million unamortized debt discount of the Convertible Notes as of September 30, 2022, offset by the $7.6 million interest expense recorded in net loss of three months ended September 30, 2022. Adjustment for the nine months ended September 30, 2022 includes write-off of $62.3 million unamortized debt discount of the Convertible Notes as of December 31, 2021, offset by the $22.2 million interest expense recorded in net loss of nine months ended September 30, 2022.
Potentially Dilutive Securities Excluded from the Diluted Per Share Calculation	The potentially dilutive securities were as follows (in thousands): September 30, 2022 Stock options and RSUs to purchase common stock 23,097 Warrants to purchase common stock 1 23,098

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($) business_unit business_line segment	Dec. 31, 2021 USD ($)	Oct. 29, 2021 $ / shares	Jun. 14, 2021
Accounting Policies [Abstract]
Common stock exchange ratio				0.8925
Redemption price (in dollars per share) | $ / shares			$ 0.10
Accumulated deficit	$ (1,015,185)	$ (858,225)
Cash and cash equivalents and short-term investments	$ 408,500
Number of reportable segments | segment	1
Number of business units | business_unit	2
Number of business lines | business_line	3

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Revenue Disaggregated by Geography (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 96,223	$ 61,941	$ 229,368	$ 174,449
United States
Disaggregation of Revenue [Line Items]
Total revenue	82,040	59,482	195,680	163,972
Rest of World
Disaggregation of Revenue [Line Items]
Total revenue	$ 14,183	$ 2,459	$ 33,688	$ 10,477

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Credit Risk and Concentration (Details) - Customer Concentration Risk - customer	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenue
Concentration Risk [Line Items]
Number of customers accounted for 10% or more	2	2	2	0
Revenue | Customers Accounted For Greater Than 10%
Concentration Risk [Line Items]
Concentration risk percentage	40%	30%	27%	0%
Accounts Receivable
Concentration Risk [Line Items]
Number of customers accounted for 10% or more			2		1
Accounts Receivable | Customers Accounted For Greater Than 10%
Concentration Risk [Line Items]
Concentration risk percentage			40%		18%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Deferred Revenue (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Change In Contract With Customer, Asset and Liability [Roll Forward]
Deferred revenue	$ 36,406
Revenue recognized from beginning balance during the nine months ended September 30, 2022	(10,972)
Deferred revenue added during the nine months ended September 30, 2022	16,073
Deferred revenue	$ 41,507

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Revenue Recognition (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) business_line business_unit	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Disaggregation of Revenue [Line Items]
Leasing revenue	$ 200	$ 500	$ 900	$ 1,600
Total revenue	96,223	61,941	229,368	174,449
Contract assets	10,200		10,200		$ 1,300
Remaining performance obligation	$ 413,800		$ 413,800
Number of business units | business_unit			2
Number of business lines | business_line			3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Remaining performance obligation, percentage	85%		85%
Remaining performance obligation, term	12 months		12 months
Charging systems and installation
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,700	200	$ 5,800	5,300
Extended warranty
Disaggregation of Revenue [Line Items]
Total revenue	$ 400	$ 600	$ 1,500	$ 1,300

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Revenue of Business Units (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 96,223	$ 61,941	$ 229,368	$ 174,449
Proterra Transit
Disaggregation of Revenue [Line Items]
Total revenue	56,363	50,175	142,563	140,187
Proterra Powered & Energy
Disaggregation of Revenue [Line Items]
Total revenue	$ 39,860	$ 11,766	$ 86,805	$ 34,262

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Product Warranties (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty reserve - beginning of period	$ 23,274
Warranty costs incurred	(6,759)
Net changes in liability for pre-existing warranties, including expirations	(2,625)
Provision for warranty	11,153
Warranty reserve - end of period	$ 25,043

Reverse Recapitalization - Narr

Reverse Recapitalization - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended	9 Months Ended
	Jun. 14, 2021 USD ($) day $ / shares shares	Jul. 31, 2021 shares	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($)	Dec. 31, 2021 shares	Jun. 13, 2021 $ / shares shares
Schedule Of Reverse Recapitalization [Line Items]
Common stock exchange ratio	0.8925
Stock converted (in shares)	123,752,882
Debt amount converted | $			$ 0	$ 48,607
Common stock reserved for issuance (in shares)	22,532,619		85,377,000
Stock converted (in shares)	34,671,900
Warrants converted (in shares)	21,424,994
Convertible securities, period from merger closing	5 years
Convertible securities, additional common stock issuable (in shares)	22,809,500
Threshold trading days | day	20
Threshold consecutive trading days | day	30
Stock price threshold for additional common stock issuable (in dollars per share) | $ / shares	$ 15
Stock price threshold for additional common stock issuable, change of control (in dollars per share) | $ / shares	$ 15
Merger Agreement, sponsor stock minimum percentage	10%
Common stock, shares outstanding (in shares)	207,348,000		225,532,429		221,960,000
Additional shares issuable, term	5 years
Capital stock, shares authorized (in shares)	510,000,000					271,920,636
Capital stock, par value (in dollars per share) | $ / shares	$ 0.0001					$ 0.0001
Common stock, shares authorized (in shares)	500,000,000		500,000,000		500,000,000	156,276,750
Preferred stock, shares authorized (in shares)	10,000,000		10,000,000		10,000,000	115,643,886
Common stock, shares issued (in shares)	207,300,000		225,532,429		221,960,000
Preferred stock, shares issued (in shares)	0		0		0
Preferred stock, shares outstanding (in shares)	0		0		0
Warrant to purchase shares of convertible preferred stock (in shares)	24,900,000
Aggregate cash proceeds received, net | $	$ 649,300
PIPE investment fees | $	13,800
Transaction costs | $	18,500
Deferred underwriting fees payable | $	9,700
Other accrued expenses | $	1,300
Related party payable | $	$ 100
Deferred transaction costs | $				$ 2,900
Reverse Recapitalization, Additional Common Shares Issuable Scenario One
Schedule Of Reverse Recapitalization [Line Items]
Percentage of additional common stock issuable	21.0526%
Stock price threshold for additional common stock issuable (in dollars per share) | $ / shares	$ 15
Stock price threshold for additional common stock issuable, change of control (in dollars per share) | $ / shares	$ 15
Reverse Recapitalization, Additional Common Shares Issuable Scenario Two
Schedule Of Reverse Recapitalization [Line Items]
Percentage of additional common stock issuable	26.3158%
Stock price threshold for additional common stock issuable (in dollars per share) | $ / shares	$ 20
Stock price threshold for additional common stock issuable, change of control (in dollars per share) | $ / shares	$ 20
Reverse Recapitalization, Additional Common Shares Issuable Scenario Three
Schedule Of Reverse Recapitalization [Line Items]
Percentage of additional common stock issuable	26.3158%
Stock price threshold for additional common stock issuable (in dollars per share) | $ / shares	$ 25
Stock price threshold for additional common stock issuable, change of control (in dollars per share) | $ / shares	$ 25
Reverse Recapitalization, Additional Common Shares Issuable Scenario Four
Schedule Of Reverse Recapitalization [Line Items]
Percentage of additional common stock issuable	26.3158%
Stock price threshold for additional common stock issuable (in dollars per share) | $ / shares	$ 30
Stock price threshold for additional common stock issuable, change of control (in dollars per share) | $ / shares	$ 30
Milestone Options
Schedule Of Reverse Recapitalization [Line Items]
Number of shares that fully vested (in shares)	669,375
Legacy warrants
Schedule Of Reverse Recapitalization [Line Items]
Common stock reserved for issuance (in shares)	3,504,523
Public warrants
Schedule Of Reverse Recapitalization [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares)	13,900,000
Private placement warrants
Schedule Of Reverse Recapitalization [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares)	7,600,000
Proterra warrants
Schedule Of Reverse Recapitalization [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares)	3,500,000
2021 Equity Incentive Plan
Schedule Of Reverse Recapitalization [Line Items]
Common stock reserved for issuance (in shares)	10,400,000		20,455,000
2010 Equity Incentive Plan
Schedule Of Reverse Recapitalization [Line Items]
Common stock reserved for issuance (in shares)	22,500,000		17,072,000
Employee Stock Purchase Plan
Schedule Of Reverse Recapitalization [Line Items]
Common stock reserved for issuance (in shares)	1,600,000
Common Stock
Schedule Of Reverse Recapitalization [Line Items]
Conversion of convertible securities (in shares)	7,400,000
Stock Options, Warrants, and Contingent Shares
Schedule Of Reverse Recapitalization [Line Items]
Common stock reserved for issuance (in shares)	82,300,000
Proterra Common Stock
Schedule Of Reverse Recapitalization [Line Items]
Stock issued, contingent consideration (in shares)		4,800,563
Sponsor Contingent Shares
Schedule Of Reverse Recapitalization [Line Items]
Stock issued, contingent consideration (in shares)		679,750
ArcLight
Schedule Of Reverse Recapitalization [Line Items]
Number of shares redeemed (in shares)	15,172
Value of stocks redeemed | $	$ 200
Common stock, shares outstanding (in shares)						27,750,000
Convertible Notes
Schedule Of Reverse Recapitalization [Line Items]
Debt amount converted | $	$ 46,500
ArcLight board of directors
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)	140,000
PIPE offering
Schedule Of Reverse Recapitalization [Line Items]
Issuance of stock (in shares)	41,500,000
Issuance of stock, price (in dollars per share) | $ / shares	$ 10
Issuance of stock, proceeds | $	$ 415,000

Reverse Recapitalization - Shar

Reverse Recapitalization - Shares Issued in Merger (Details) - shares	Jun. 14, 2021	Jun. 13, 2021	Sep. 30, 2022	Dec. 31, 2021
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)	207,348,000		225,532,429	221,960,000
Sponsor (in shares)	6,257,000
Sponsor Earnout Stock (in shares)	680,000
ArcLight Shareholders
Schedule Of Reverse Recapitalization [Line Items]
Issuance of stock (in shares)	34,672,000
PIPE Investors
Schedule Of Reverse Recapitalization [Line Items]
Issuance of stock (in shares)	41,500,000
Legacy Proterra Investors
Schedule Of Reverse Recapitalization [Line Items]
Issuance of stock (in shares)	131,176,000
ArcLight
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)		27,750,000
Less redemption of ArcLight shares (in shares)		(15,000)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Total	$ 401,596	$ 643,941
Fair Value, Recurring | Level 1 | U.S. Treasury securities
Assets:
Short-term investments	348,938	330,053
Fair Value, Recurring | Level 1 | Money market funds
Assets:
Cash equivalents and marketable securities	44,696	102,978
Fair Value, Recurring | Level 1 | U.S. Treasury securities
Assets:
Cash equivalents and marketable securities	7,962	49,996
Fair Value, Recurring | Level 2 | Corporate debt securities
Assets:
Short-term investments	$ 0	$ 160,914

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	$ 52,658	$ 152,974
Unrealized Losses	(2,069)	(588)
Amortized Cost	403,665	644,529
Estimated Fair Value	401,596	643,941
Cash equivalents: | Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	44,696	102,978
Cash equivalents: | U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	7,962	49,996
Short-term investments: | U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	351,007	330,618
Unrealized Losses	(2,069)	(565)
Estimated Fair Value	$ 348,938	330,053
Short-term investments: | Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		160,937
Unrealized Losses		(23)
Estimated Fair Value		$ 160,914

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Long-term investments	$ 26,600
Equity investment	25,000
Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized debt discount and issuance costs	51,890	$ 62,327
Convertible Notes | Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt	213,600
Convertible Notes | Carrying value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt	$ 117,000

Balance Sheet Components - Cash

Balance Sheet Components - Cash and Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents
Cash	$ 6,952	$ 17,065
Cash equivalents	52,658	152,974
Total cash and cash equivalents	59,610	170,039
Cash, Cash Equivalents, and Restricted Cash
Cash and cash equivalents	59,610	170,039
Restricted cash, current portion	12,105	12,105
Restricted cash, net of current portion	460	460
Total restricted cash	12,565	12,565
Total cash and cash equivalents, and restricted cash	$ 72,175	$ 182,604	$ 293,102	$ 123,697

Balance Sheet Components - Inve

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 110,185		$ 110,185		$ 65,225
Work in progress	29,470		29,470		25,062
Finished goods	18,044		18,044		18,269
Service parts	7,135		7,135		6,000
Total inventories	164,834		164,834		$ 114,556
Write-down of inventories	$ 0	$ 600	$ 0	$ 1,300

Balance Sheet Components - Prop

Balance Sheet Components - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Finance lease right-of-use assets	$ 179		$ 179		$ 179
Property, plant and equipment, and finance lease right-of-use asset gross	157,337		157,337		120,905
Less: Accumulated depreciation and amortization	(63,681)		(63,681)		(58,659)
Total	93,656		93,656		62,246
Depreciation and amortization expense	2,900	$ 3,900	9,583	$ 11,675
Computer hardware
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,273		5,273		5,195
Computer software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,753		9,753		9,561
Internally used vehicles and charging systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,761		14,761		16,459
Leased vehicles and batteries
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,142		5,142		6,863
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,679		10,679		10,516
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28,575		28,575		28,302
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,942		1,942		1,861
Tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	21,859		21,859		21,726
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 59,174		$ 59,174		$ 20,243

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related expenses	$ 10,821	$ 8,069
Accrued sales and use tax	1,102	885
Warranty reserve	8,413	8,116
Other accrued expenses	5,583	3,564
Total	$ 25,919	$ 20,634

Balance Sheet Components - Othe

Balance Sheet Components - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Warranty reserve	$ 16,630	$ 15,158
Finance lease liabilities, non-current	65	87
Total	$ 16,695	$ 15,245

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Total debt	$ 116,995	$ 110,999
Less debt, current	0	0
Debt, non-current	116,995	110,999
PPP loan
Debt Instrument [Line Items]
Total debt	0	10,000
Convertible Notes
Debt Instrument [Line Items]
Total debt	$ 116,995	$ 100,999

Debt - Senior Credit Facility (

Debt - Senior Credit Facility (Details) - USD ($)	1 Months Ended
	May 31, 2019	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Amount outstanding		$ 116,995,000	$ 110,999,000
Letters of credit outstanding, amount		16,100,000
Senior Credit Facility
Debt Instrument [Line Items]
Borrowing capacity	$ 75,000,000
Availability, period from maturity of subordinated debt	91 days
Availability, subordinated debt	$ 7,500,000
Commitment potential increase	50,000,000
Commitment potential reduction	$ 25,000,000
Termination notice period	15 days
Fixed Charge Coverage Ratio	1
Amount outstanding		0	$ 0
Letters of credit outstanding, amount		$ 15,900,000
Senior Credit Facility | Federal Funds Rate | Variable rate component one
Debt Instrument [Line Items]
Spread on variable interest rate	0.50%
Senior Credit Facility | London Interbank Offered Rate (LIBOR) | Variable rate component one
Debt Instrument [Line Items]
Spread on variable interest rate	1%
Senior Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum | Variable rate component two
Debt Instrument [Line Items]
Spread on variable interest rate	1.50%
Senior Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum | Variable rate component two
Debt Instrument [Line Items]
Spread on variable interest rate	3%
Senior Credit Facility | Base Rate | Minimum | Variable rate component two
Debt Instrument [Line Items]
Spread on variable interest rate	0%
Senior Credit Facility | Base Rate | Maximum | Variable rate component two
Debt Instrument [Line Items]
Spread on variable interest rate	1.50%
Letter of credit
Debt Instrument [Line Items]
Borrowing capacity	$ 20,000,000

Debt - Small Business Administr

Debt - Small Business Administration Loan (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	May 31, 2022	May 31, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Gain on debt extinguishment			$ 0	$ 0	$ 10,201	$ 0
PPP loan
Debt Instrument [Line Items]
Loan proceeds		$ 10,000
Debt forgiven	$ 10,000
Interest refunded	200
Gain on debt extinguishment	$ 10,200

Debt - Convertible Notes (Detai

Debt - Convertible Notes (Details) - USD ($) $ / shares in Units, shares in Millions		3 Months Ended		9 Months Ended
	Jun. 14, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Aug. 31, 2020
Debt Instrument [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares)	24.9
Debt amount converted				$ 0	$ 48,607,000
Conversion of Convertible Notes into common stock					48,781,000
Amortization of debt issuance cost and debt discounts				10,497,000	31,519,000
Convertible Debt [Abstract]
Total debt		$ 116,995,000		$ 116,995,000		$ 110,999,000
Additional Paid-in Capital
Debt Instrument [Line Items]
Conversion of Convertible Notes into common stock					48,780,000
Convertible note warrants
Debt Instrument [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares)							4.6
Exercise price of warrants (in dollars per share)							$ 0.02
Warrant liability							$ 29,000,000
Fair value of embedded derivative liability							68,500,000
Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount							$ 200,000,000
Interest rate							5%
Paid-in-kind interest rate							4.50%
Conversion terms, event of liquidation or sale, conversion price percentage							150%
Covenant, required minimum liquidity							$ 75,000,000
Covenant, required minimum liquidity, multiple factor of cash burn							4
Debt issuance costs incurred							$ 5,100,000
Debt amount converted	$ 46,500,000
Write off of unamortized debt issuance cost	21,000,000
Convertible Notes, conversion price (in usd per share)		$ 6.5712		$ 6.5712
VWAP (in usd per share)		$ 9.86		$ 9.86
Consecutive days				20 days
Amortization of debt issuance cost and debt discounts		$ 3,600,000	$ 3,200,000	$ 10,400,000	$ 31,500,000
Convertible Debt [Abstract]
Principal		153,500,000		153,500,000		153,500,000
PIK interest		15,385,000		15,385,000		9,826,000
Total principal		168,885,000		168,885,000		163,326,000
Less debt discount and issuance costs		(51,890,000)		(51,890,000)		(62,327,000)
Total debt		$ 116,995,000		$ 116,995,000		$ 100,999,000
Convertible Notes | Additional Paid-in Capital
Debt Instrument [Line Items]
Conversion of Convertible Notes into common stock	$ 48,800,000

Debt - Future Principal Repayme

Debt - Future Principal Repayments (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2022	$ 0
2025	168,885
Total debt	$ 168,885

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Leases [Abstract]
Operating lease, expense	$ 1.9	$ 1	$ 5.4	$ 3
Operating lease, weighted average remaining lease term	6 years 7 months 6 days		6 years 7 months 6 days		7 years 7 months 6 days
Operating lease, weighted average discount rate, percent	5.70%		5.70%		5.80%

Leases - Net Investment In Leas

Leases - Net Investment In Lease (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Leases [Abstract]
Net investment in leases, current	$ 658	$ 411
Net investment in leases, non-current	8,722	5,179
Total net investment in leases	$ 9,380	$ 5,590

Leases - Lessor Future Minimum

Leases - Lessor Future Minimum Payments Receivable (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Operating leases
Remainder of 2022	$ 175
2023	384
2024	0
2025	0
2026	0
Thereafter	0
Total minimum lease payments	559
Sales-type leases
Remainder of 2022	145
2023	749
2024	1,010
2025	1,528
2026	1,528
Thereafter	5,541
Total minimum lease payments	$ 10,501

Leases - Maturities Of Operatin

Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Leases [Abstract]
Remainder of 2022	$ 2,065
2023	6,893
2024	4,224
2025	3,487
2026	2,615
Thereafter	12,096
Total undiscounted lease payment	31,380
Less: imputed interest	(6,034)
Total operating lease liabilities	$ 25,346	$ 25,047

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ (4,822)	$ (3,050)

Leases - Operating Lease Right-

Leases - Operating Lease Right-of-use Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Operating leases
Operating lease right-of-use assets	$ 24,169	$ 24,282
Operating lease liabilities, current	6,354	4,084
Operating lease liabilities, non-current	18,992	20,963
Total operating lease liabilities	$ 25,346	$ 25,047

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Purchase commitment, outstanding inventory and other	$ 2,300,000
Long-term prepayment	10,000	$ 0
Letters of credit outstanding, amount	$ 16,100

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details)	9 Months Ended
	Sep. 30, 2022 vote shares	Dec. 31, 2021 shares	Jun. 14, 2021 $ / shares shares	Jun. 13, 2021 $ / shares shares
Equity [Abstract]
Capital stock, shares authorized (in shares)			510,000,000	271,920,636
Capital stock, par value (in dollars per share) | $ / shares			$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000	500,000,000	156,276,750
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000	10,000,000	115,643,886
Common stock, shares issued (in shares)	225,532,429	221,960,000	207,300,000
Common stock, shares outstanding (in shares)	225,532,429	221,960,000	207,348,000
Preferred stock, shares issued (in shares)	0	0	0
Preferred stock, shares outstanding (in shares)	0	0	0
Common stock, number of votes per share | vote	1
Common stock exchange ratio			0.8925

Stockholders' Equity - Reserved

Stockholders' Equity - Reserved Shares (Details) - shares	Sep. 30, 2022	Jun. 14, 2021
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	85,377,000	22,532,619
2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	3,524,000
Warrants
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	1,000
Earnout Stock
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	18,009,000
Convertible notes
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	26,316,000
2010 Equity Incentive Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	17,072,000	22,500,000
2021 Equity Incentive Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	20,455,000	10,400,000

Equity Plans and Stock-based _3

Equity Plans and Stock-based Compensation - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended			9 Months Ended
	Jun. 14, 2021	Jun. 11, 2021	Jun. 30, 2021	Mar. 31, 2020	Sep. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Number of options (in shares)					11,757,906			11,757,906
Stock-based compensation expense					$ 5,356,000		$ 3,178,000	$ 16,313,000	$ 11,265,000
Awards granted (in shares)								758,528
Awards outstanding (in shares)					14,685,863			14,685,863		18,101,584
Total intrinsic value of stock options exercised								$ 10,000,000
Total estimated grant date fair value of stock options vested								7,400,000
Unrecognized stock-based compensation expense, stock options					$ 15,200,000			$ 15,200,000
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Number of options (in shares)	22,532,619
Common stock reserved for the Plan (in shares)		387,531
2021 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for the Plan (in shares)		10,000,000
Annual percentage increase in shares reserved		4%
Additional shares reserved (in shares)						8,878,388
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for the Plan (in shares)		1,630,000
Annual percentage increase in shares reserved		1%
Additional shares reserved (in shares)						2,219,597
Number of shares that may be issued (in shares)		16,300,000
ESPP, purchase price percentage								15%
ESPP, purchase price of common stock, percentage								85%
ESPP, maximum shares that may be purchased (in shares)								2,500
ESPP, offering period								6 months
ESPP, maximum amount that may be purchased								$ 25,000
Stock-based compensation expense								$ 1,000,000
Stock issuance for employee stock purchase plan (in shares)					325,106
Purchase price of common stock issued under the ESPP (in dollars per share)					$ 4.62
2010 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Number of options (in shares)					17,072,030			17,072,030
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period								4 years
Unrecognized stock-based compensation expense, period for recognition								2 years
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period								4 years
Unrecognized stock-based compensation expense, period for recognition								3 years 2 months 12 days
Unrecognized stock-based compensation expense, RSUs					$ 33,000,000			$ 33,000,000
CEO Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)				4,685,624
CEO Time-Based Awards tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Awards granted (in shares)				1,338,749
Award exercise price (in dollars per share)				$ 5.33
CEO Time-Based Awards tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Awards outstanding (in shares)				2,677,500						2,677,500
CEO Time-Based Awards tranche two | Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award exercise price (in dollars per share)				$ 11.21
CEO Time-Based Awards tranche two | Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award exercise price (in dollars per share)				16.81
CEO Time-Based Awards tranche two | Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award exercise price (in dollars per share)				22.41
CEO Time-Based Awards tranche two | Tranche Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award exercise price (in dollars per share)				28.02
Milestone Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 2,100,000
Award exercise price (in dollars per share)				$ 5.33
Awards outstanding (in shares)				669,375						669,375
Number of shares that fully vested (in shares)	669,375

Equity Plans and Stock-based _4

Equity Plans and Stock-based Compensation - Outstanding Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2020	Sep. 30, 2022	Dec. 31, 2021
Number of Stock Options Outstanding
Balance at beginning of period (in shares)		18,101,584
Granted (in shares)		758,528
Exercised (in shares)		(2,912,066)
Cancelled/forfeited/expired (in shares)		(1,262,183)
Balance at end of period (in shares)		14,685,863	18,101,584
Options exercisable, Number of options (in shares)		11,757,906
Weighted- Average Exercise Price
Balance at beginning of period (in dollars per share)		$ 4.08
Granted (in dollars per share)		7.70
Exercised (in dollars per share)		3.04
Cancelled/forfeited/expired (in dollars per share)		6.10
Balance at end of period (in dollars per share)		4.30	$ 4.08
Options exercisable, Weighted average exercise price per share (in dollars per share)		$ 3.80
Stock Options, Additional Disclosures
Options outstanding, Weighted average remaining contractual term		5 years 8 months 12 days	5 years 6 months
Options exercisable, Weighted average remaining contractual term		5 years
Options outstanding, Aggregate intrinsic value		$ 17,159	$ 87,425
Options exercisable, Aggregate intrinsic value		$ 16,790
CEO Time-Based Awards tranche two
Number of Stock Options Outstanding
Balance at beginning of period (in shares)		2,677,500
Balance at end of period (in shares)	2,677,500		2,677,500
Milestone Options
Number of Stock Options Outstanding
Balance at beginning of period (in shares)		669,375
Balance at end of period (in shares)	669,375		669,375
Equity Awards
Number of Stock Options Outstanding
Balance at end of period (in shares)		1,673,436
Weighted- Average Exercise Price
Options exercisable, Weighted average exercise price per share (in dollars per share)		$ 19.61

Equity Plans and Stock-based _5

Equity Plans and Stock-based Compensation - Assumptions Used in Fair Value Measurement (Details) - Stock options	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 3 months 18 days	6 years 2 months 12 days
Risk-free interest rate	2%	1%
Expected volatility	55.10%	53.90%
Expected dividend rate	0%	0%

Equity Plans and Stock-based _6

Equity Plans and Stock-based Compensation - RSU Activity (Details) - Restricted stock units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Number of RSUs
Balance at beginning of period (in shares)	1,324,960
Granted (in shares)	4,589,454
Released (in shares)	(335,546)
Forfeited (in shares)	(514,260)
Balance at end of period (in shares)	5,064,608
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share)	$ 10.67
Granted (in dollars per share)	6.91
Released (in dollars per share)	10.25
Forfeited (in dollars per share)	8.96
Balance at end of period (in dollars per share)	$ 7.46
Aggregate intrinsic value	$ 25,222	$ 11,699

Equity Plans and Stock-based _7

Equity Plans and Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 5,356	$ 3,178	$ 16,313	$ 11,265
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	456	319	1,350	865
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	1,409	567	3,690	1,625
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 3,491	$ 2,292	$ 11,273	$ 8,775

Net Income (Loss) Per Share - C

Net Income (Loss) Per Share - Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021
Numerator:
Net income (loss)	$ (65,061)	$ 36,321	$ (156,960)	$ (204,868)
Effect of dilutive securities:
Gain on valuation of warrant liabilities	0	(73,197)	0	0
Interest expense to be recognized upon conversion of Convertible Notes	(47,891)	(61,774)	(40,154)	0
Numerator for diluted EPS - Net loss after the effect of dilutive securities	$ (112,952)	$ (98,650)	$ (197,114)	$ (204,868)
Denominator:
Weighted-average shares used in computing net loss per share of common stock, basic (in shares)	225,291	212,071	223,782	89,233
Dilutive impact of public and private placement warrants (in shares)	0	594	0	0
Convertible Notes (in shares)	25,413	24,300	24,855	0
Diluted weighted average shares (in shares)	250,704	236,965	248,637	89,233
Net income (loss) per share of common stock:
Basic (in dollars per share)	$ (0.29)	$ 0.17	$ (0.70)	$ (2.30)
Diluted (in dollars per share)	$ (0.45)	$ (0.42)	$ (0.79)	$ (2.30)
Debt Instrument [Line Items]
Interest expense	$ 7,600		$ 22,200
Convertible Notes
Debt Instrument [Line Items]
Unamortized debt discount					$ 55,500	$ 62,300

Net Income (Loss) Per Share - N

Net Income (Loss) Per Share - Narrative (Details)	9 Months Ended
	Sep. 30, 2022 $ / shares	Jun. 14, 2021
Earnings Per Share [Abstract]
Common stock exchange ratio		0.8925
Convertible Notes
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share)	$ 6.5712
VWAP (in usd per share)	$ 9.86
Consecutive days	20 days

Net Income (Loss) Per Share - P

Net Income (Loss) Per Share - Potentially Dilutive Securities (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2022 shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	23,098
Stock options and RSUs to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	23,097
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	1

401(k) Plan (Details)

401(k) Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Retirement Benefits [Abstract]
Employer matching contribution, percent of match			4%
Employer matching contribution, cost	$ 0.9	$ 0.6	$ 2.4	$ 1.8