Proterra (PTRAQ) 10-Q 10 May 23 2023 Q1 Quarterly report Financial data

Cover

Cover - shares shares in Millions	3 Months Ended
	Mar. 31, 2023	May 05, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
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	90-2099565
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		226.9
Entity Central Index Key	0001820630
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	[1]
Assets:
Cash and cash equivalents	$ 167,905	$ 73,695
Accounts receivable, net	98,715	130,337
Short-term investments	128,341	224,359
Inventory	205,489	169,567
Prepaid expenses and other current assets	37,897	50,893
Deferred cost of goods sold	3,456	4,304
Restricted cash, current	12,565	12,565
Total current assets	654,368	665,720
Property, plant, and equipment, net	110,425	107,552
Operating lease right-of-use assets	18,661	20,274
Long-term inventory prepayment	10,000	10,000
Other assets	37,261	36,913
Total assets	830,715	840,459
Liabilities and Stockholders’ Equity:
Accounts payable	92,158	57,822
Accrued liabilities	25,262	33,551
Deferred revenue, current	35,401	30,017
Operating lease liabilities, current	5,998	6,876
Debt, current	177,735	122,692
Derivative liability	135,678	0
Total current liabilities	472,232	250,958
Deferred revenue, non-current	49,994	37,381
Operating lease liabilities, non-current	17,241	18,098
Other long-term liabilities	20,532	17,164
Total liabilities	559,999	323,601
Commitments and contingencies (Note 6)
Stockholders’ equity:
Common stock, $0.0001 par value; 500,000 shares authorized and 226,853 shares issued and outstanding as of March 31, 2023 (unaudited); 500,000 shares authorized and 226,265 shares issued and outstanding as of December 31, 2022	22	22
Preferred stock, $0.0001 par value; 10,000 shares authorized and zero shares issued and outstanding as of March 31, 2023 (unaudited); 10,000 shares authorized, zero shares issued and outstanding as of December 31, 2022	0	0
Additional paid-in capital	1,610,783	1,613,556
Accumulated deficit	(1,340,152)	(1,096,175)
Accumulated other comprehensive loss	63	(545)
Total stockholders’ equity	270,716	516,858
Total liabilities and stockholders’ equity	$ 830,715	$ 840,459
[1]Derived from audited Consolidated Financial Statements.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
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)	226,852,590	226,265,000
Common stock, shares outstanding (in shares)	226,852,590	226,265,000
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
	Mar. 31, 2023	Mar. 31, 2022
Total revenue	$ 79,529	$ 58,581
Total cost of goods sold	86,087	61,584
Gross loss	(6,558)	(3,003)
Research and development	18,524	11,802
Selling, general and administrative	35,886	28,387
Total operating expenses	54,410	40,189
Loss from operations	(60,968)	(43,192)
Interest expense, net	7,254	6,879
Loss on debt extinguishment	177,939	0
Other expense (income), net	(2,184)	7
Loss before income taxes	(243,977)	(50,078)
Provision for income taxes	0	0
Net loss	$ (243,977)	$ (50,078)
Net loss per share of common stock:
Basic (in dollars per share)	$ (1.08)	$ (0.23)
Diluted (in dollars per share)	$ (1.08)	$ (0.43)
Weighted average shares used in per share computation:
Basic (in shares)	226,410	222,276
Diluted (in shares)	226,410	247,131
Product
Total revenue	$ 69,996	$ 54,171
Total cost of goods sold	79,051	57,226
Parts and other service
Total revenue	9,533	4,410
Total cost of goods sold	$ 7,036	$ 4,358

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net loss	$ (243,977)	$ (50,078)
Available-for-sales securities:
Unrealized gain (loss) on available-for-sale securities	608	(1,641)
Other comprehensive income (loss), net of taxes	608	(1,641)
Total comprehensive loss, net of taxes	$ (243,369)	$ (51,719)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total		Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2021			221,960
Beginning balance at Dec. 31, 2021	$ 720,152		$ 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)			743
Issuance of stock upon exercise of options and RSU release	1,833			1,833
Stock-based compensation	4,642			4,642
Net income (loss)	(50,078)				(50,078)
Other comprehensive gain (loss), net of taxes	(1,641)					(1,641)
Ending balance (in shares) at Mar. 31, 2022			222,703
Ending balance at Mar. 31, 2022	674,908		$ 22	1,585,418	(908,303)	(2,229)
Beginning balance (in shares) at Dec. 31, 2022			226,265
Beginning balance at Dec. 31, 2022	516,858	[1]	$ 22	1,613,556	(1,096,175)	(545)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock upon exercise of options and warrants (in shares)			588
Issuance of stock upon exercise of options and RSU release	113			113
Stock-based compensation	4,314			4,314
Debt extinguishment fair value adjustment	(7,200)			(7,200)
Net income (loss)	(243,977)				(243,977)
Other comprehensive gain (loss), net of taxes	608					608
Ending balance (in shares) at Mar. 31, 2023			226,853
Ending balance at Mar. 31, 2023	$ 270,716		$ 22	$ 1,610,783	$ (1,340,152)	$ 63
[1]Derived from audited Consolidated Financial Statements.

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss	$ (243,977)	$ (50,078)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	4,717	3,381
Stock-based compensation	4,314	4,642
Amortization of debt discount and issuance costs	3,854	3,337
Accretion of debt PIK interest	1,895	1,812
Loss on debt extinguishment	177,939	0
Others	(1,101)	494
Changes in operating assets and liabilities:
Accounts receivable	31,622	3,287
Inventory	(35,922)	(13,830)
Prepaid expenses and other current assets	12,996	333
Deferred cost of goods sold	849	(824)
Operating lease right-of-use assets and liabilities	(123)	4
Other assets	(367)	309
Accounts payable and accrued liabilities	29,501	(3,485)
Deferred revenue, current and non-current	17,997	(1,664)
Other non-current liabilities	2,913	134
Net cash provided by (used in) operating activities	7,107	(52,148)
Cash flows from investing activities:
Purchase of investments	(76,121)	(202,479)
Proceeds from maturities of investments	174,000	140,000
Purchase of property and equipment	(8,451)	(9,173)
Net cash provided by (used in) investing activities	89,428	(71,652)
Cash flows from financing activities:
Proceeds from (repayment of) government grants	0	(700)
Proceeds from exercise of stock options	113	1,833
Other financing activities	(2,438)	(8)
Net cash provided by (used in) financing activities	(2,325)	1,125
Net increase (decrease) in cash and cash equivalents, and restricted cash	94,210	(122,675)
Cash and cash equivalents, and restricted cash at the beginning of period	86,260	182,604
Cash and cash equivalents, and restricted cash at the end of period	180,470	59,929
Supplemental disclosures of cash flow information:
Cash paid for interest	2,164	2,094
Cash paid for income taxes	0	0
Non-cash investing and financing activity:
Assets acquired through accounts payable and accrued liabilities	$ 2,704	$ 7,087

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Organization and Description of Business Proterra Inc (“Proterra” or the “Company") is a leading developer and producer of zero-emission electric vehicle and EV technology solutions for commercial application. 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. Proterra is headquartered in Burlingame, California, and has manufacturing and product development facilities in Burlingame and City of Industry, California, and Greenville and Greer, South Carolina. Proterra Operating Company, Inc. (“Proterra OpCo” and formerly known as Proterra Inc prior to the consummation of the Business Combination (“Legacy Proterra”)) was originally formed in June 2004 as a Colorado limited liability company and converted to a Delaware corporation in February 2010. On June 14, 2021, Legacy Proterra consummated the transactions contemplated by the Merger Agreement, by and among ArcLight Clean Transition Corp. (“ArcLight”), (and, after the Domestication, Proterra), Phoenix Merger Sub, and Legacy Proterra, whereby Phoenix Merger Sub merged with and into Legacy Proterra, and Legacy Proterra being the surviving corporation and a wholly owned subsidiary of Proterra. Legacy Proterra changed its name to “Proterra Operating Company, Inc.” and continues as a Delaware Corporation. 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. The Company has incurred net losses and negative cash flows from operations since inception. As of March 31, 2023, the Company has an accumulated deficit of $1.3 billion, and cash and cash equivalents and short-term investments of $296.2 million. The Company has funded operations primarily through a combination of equity and debt financing. There was no outstanding balance under the Senior Credit Facility as of March 31, 2023. There was an aggregate of $20.1 million of letters of credit outstanding under the Senior Credit Facility as of March 31, 2023. As of March 31, 2023, the outstanding balance of the Convertible Notes Facility was $172.9 million inclusive of PIK interest of $19.4 million. As of March 31, 2023, the Company had $296.2 million of cash and cash equivalents and short-term investments. The audit report included in the Annual Report on Form 10-K (the “2022 Financials”) contained a going concern qualification, which is an event of default under both the Senior Credit Facility and the Convertible Notes Facility. On March 14, 2023, the Company obtained a limited advance waiver from the holders of the Convertible Notes with respect to the Going Concern Covenant until March 31, 2023. On March 31, 2023, the Company received a waiver for the Senior Credit Facility to consent to the delivery of the 2022 Financials with a going concern qualification and waived the cross default of the corresponding covenant under the Convertible Notes Facility in connection with the 2022 Financials. As a result, the Company was in compliance with the covenants contained in the Senior Credit Facility and Convertible Notes Facility as of March 31, 2023. On March 31, 2023, the Company also entered into an amendment to the Convertible Notes Facility, which provides a waiver of the Minimum Liquidity Covenant (as defined below) through May 31, 2024, requiring a minimum Liquidity (as defined in the Note Purchase Agreement) of $125.0 million as of the last day of each quarter from March 31, 2023 through and including May 31, 2024, and a waiver of the requirement that the financial statements delivered by the Company be certified by the Company’s auditor without qualification (or similar notation) as to going concern for the Company’s consolidated financial statements for fiscal years 2022 and 2023. After May 31, 2024, the Convertible Notes Facility requires the Company to maintain Liquidity at each quarter end (“Minimum Liquidity Covenant”) of not less than the greater of (i) $75.0 million and (ii) four times of Cash Burn (as defined in the Note Purchase Agreement) for the three-month period then ended. See Note 4, Debt, for details of the Convertible Notes Facility. The amendment to the Convertible Notes Facility is considered an extinguishment of the existing debt, and the issuance of new debt upon the effectiveness of the amendment to the Convertible Notes Facility on March 31, 2023. The extinguishment and issuance of new debt in connection with the Convertible Notes Facility resulted in a $177.9 million loss on debt extinguishment recorded in the Company’s condensed consolidated statements of operations. The embedded features in the Convertible Notes were bifurcated and accounted for as a derivative liability separately from the host debt instrument. As of March 31, 2023, the fair value of derivative liability of $135.7 million was recorded as debt discount on the Company’s condensed consolidated balance sheets, which will be amortized during the term of the Convertible Notes to interest expense using the effective-interest method. Under ASC Subtopic 205-40, Presentation of Financial Statements—Going Concern (“ASC 205-40”), the Company has the responsibility to evaluate whether conditions and/or events raise substantial doubt about the Company’s ability to meet our future obligations as they become due within one year of the financial statements being issued in this Quarterly Report on Form 10-Q. The Company’s potential inability to maintain the Liquidity requirement under the Convertible Notes Facility and any resulting potential events of default under the Convertible Notes Facility and the Senior Credit Facility when coupled with the following conditions: the Company’s available cash resources, recurring losses and cash outflows from operations, an expectation of continuing operating losses and cash outflows from operations for the foreseeable future, and the need to raise additional capital to finance future operations, causes substantial doubt about the Company’s ability to continue as a going concern to exist. The Company is currently executing on various strategies designed to improve liquidity and cash generated from operations. The Company is undertaking expense reduction and cash savings initiatives that include streamlining facilities, initiating working capital initiatives, and reducing overall selling, general and administrative expenses that include a workforce reduction announced in January 2023, and the planned closure of the City of Industry facility by December 31, 2023 to improve operational efficiency. The Company is exploring potential options for raising additional funds through potential alternatives, which may include, among other things, the issuance of equity, equity-linked, and/or debt securities, debt financings or other capital sources and/or strategic transactions. However, we have not yet secured additional financing and may not be successful in securing additional financing or executing a transaction on a timely basis, on acceptable terms or at all. These financial statements have been prepared by management in accordance with GAAP and this basis assumes that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. 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”). 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, 2022 and the related notes incorporated by reference in the Company’s Annual Report (the “Annual Report”) on Form 10-K, filed with SEC on March 17, 2023 and amended on May 1, 2023, which provides a more complete discussion of the Company’s accounting policies and certain other information. The information as of December 31, 2022 and 2021 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 March 31, 2023 and the results of operations and cash flows for the three months ended March 31, 2023 and 2022. The results of operations for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the year ending December 31, 2023. 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 changes to the Company’s significant accounting policies described in the Annual Report, except for the accounting policies related to the Convertible Notes and derivative liabilities described in Note 4, Debt, that have had a material impact on the Company’s condensed consolidated financial statements and related notes. Segments The Company operates in the United States and has sales to the European Union, Canada, United Kingdom, Australia, Japan and Türkiye. Revenue disaggregated by geography, based on the addresses of the Company’s customers, consists of the following (in Three Months Ended March 31, 2023 2022 United States $ 65,424 $ 51,967 Rest of World 14,105 6,614 $ 79,529 $ 58,581 The Company’s chief operating decision maker is its Chief Executive Officer (CEO) who reviews financial information presented on a consolidated basis for purposes of making decision on allocating resources and assessing financial performance. 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 March 31, 2023 and December 31, 2022. 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 March 31, 2023, 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 Türkiye. 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 March 31, March 31, December 31, 2023 2022 2023 2022 Number of customers accounted for 10% or more 3 2 4 2 Total % for customers accounted for 10% or more 34% 40% 49% 48% Single source suppliers provide the Company with a number of components that are required for manufacturing of its current products. For example, we sole source our composite bus bodies from TPI Composites Inc. 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 months ended March 31, 2023 and 2022, respectively. 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, 2022 $ 67,398 Revenue recognized from beginning balance during the three months ended March 31, 2023 (6,815) Deferred revenue added during the three months ended March 31, 2023 24,812 Deferred revenue as of March 31, 2023 $ 85,395 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 $0.3 million and $0.3 million in the three months ended March 31, 2023 and 2022, 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 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 $1.2 million and $2.1 million for the three months ended March 31, 2023 and 2022, respectively. Extended warranty revenue was $0.6 million and $0.4 million for the three months ended March 31, 2023 and 2022, respectively. As of March 31, 2023 and December 31, 2022, the contract assets balance was $13.0 million and $26.1 million, respectively, and are recorded in the prepaid expenses and other current assets on the consolidated balance sheets. The contract assets are expected to be billed within the next twelve months. As of March 31, 2023, the amount of remaining performance obligations that have not been recognized as revenue was $472.9 million, of which 68% 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 has the following commercial offerings each addressing a critical component of commercial vehicle electrification. • 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 offers 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. Revenue of these commercial offerings are as follows (in thousands): Three Months Ended March 31, 2023 2022 Proterra Transit $ 44,862 $ 35,381 Proterra Powered & Energy 34,667 23,200 Total $ 79,529 $ 58,581 Product Warranties Warranty expense is recorded as a component of cost of goods sold. Accrued warranty activity consisted of the following (in thousands): Three Months Ended March 31, 2023 Warranty reserve - beginning of period $ 25,513 Warranty costs incurred (868) Net changes in liability for pre-existing warranties, including expirations — Provision for warranty 3,604 Warranty reserve - end of period $ 28,249 There have been no recent accounting pronouncements, changes in accounting pronouncements or recently adopted accounting guidance during the three months ended March 31, 2023 that are of significance or potential significance to the Company.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2023
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 and liabilities measured at fair value on a recurring basis using the above input categories were as follows (in thousands): Pricing Category Fair Value at March 31, 2023 December 31, 2022 Assets: Cash equivalents and marketable securities: Money market funds Level 1 $ 57,325 $ 14,941 U.S. Treasury securities Level 1 74,689 — Short-term investments: U.S. Treasury securities Level 1 128,341 224,359 Total $ 260,355 $ 239,300 Liabilities: Other non-current liabilities Derivative liability Level 3 $ 135,678 $ — Total $ 135,678 $ — The Company’s short-term investments were comprised of U.S. Treasury 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 March 31, 2023, 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. The long-term investment balances include $25.0 million strategic equity investment made in the third quarter of 2022 in an entity that the Company expects to produce lithium iron phosphate (LFP) battery cells in the United States in the coming years which is expected to 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 months ended March 31, 2023 and 2022. There are no unrealized gains or losses associated with these investments as of March 31, 2023. The following is a summary of cash equivalents and marketable securities as of March 31, 2023 (in thousands): Amortized Cost Unrealized Gain Estimated Fair Value Cash equivalents: Money market funds $ 57,325 $ — $ 57,325 U.S. Treasury securities 74,689 — 74,689 Short-term investments: U.S. Treasury securities 128,278 63 128,341 Total $ 260,292 $ 63 $ 260,355 As of March 31, 2023, 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, 2022 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 14,941 $ — $ 14,941 Short-term investments: U.S. Treasury securities 224,904 (545) 224,359 Total $ 239,845 $ (545) $ 239,300 As of December 31, 2022, the contractual maturities of the short-term investments were less than one year.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Cash and cash equivalents consisted of the following (in thousands): March 31, 2023 December 31, 2022 Cash $ 35,891 $ 58,754 Cash equivalents 132,014 14,941 Total cash and cash equivalents $ 167,905 $ 73,695 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. March 31, 2023 December 31, 2022 Cash and cash equivalents $ 167,905 $ 73,695 Restricted cash, current portion 12,565 12,565 Total cash and cash equivalents, and restricted cash $ 180,470 $ 86,260 Inventories consisted of the following (in thousands): March 31, 2023 December 31, 2022 Raw materials $ 163,327 $ 127,199 Work in progress 22,419 21,153 Finished goods 11,123 13,518 Service parts 8,620 7,697 Total inventories $ 205,489 $ 169,567 The write-down of excess or obsolete inventories to cost of goods sold were immaterial for the three months ended March 31, 2023 and 2022, respectively. Property, plant, and equipment, net, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Computer hardware $ 6,020 $ 5,465 Computer software 12,813 11,012 Internally used vehicles and charging systems 15,177 15,177 Leased vehicles and batteries 5,142 5,142 Leasehold improvements 30,883 10,716 Machinery and equipment 54,195 28,942 Office furniture and equipment 3,282 2,523 Tooling 23,971 22,430 Finance lease right-of-use assets 878 179 Construction in progress 29,209 72,505 181,570 174,091 Less: Accumulated depreciation and amortization (71,145) (66,539) Total $ 110,425 $ 107,552 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 months ended March 31, 2023 and 2022, depreciation and amortization expense were $4.7 million and $3.4 million, respectively. Accrued liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Accrued payroll and related expenses $ 6,493 $ 8,647 Accrued sales and use tax 1,284 1,784 Warranty reserve 8,229 8,406 Accrued supplier liability 4,059 7,699 Insurance related 1,764 4,445 Other accrued expenses 3,433 2,570 Total $ 25,262 $ 33,551 Other long-term liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Warranty reserve $ 20,020 $ 17,107 Finance lease liabilities, non-current 512 57 Total $ 20,532 $ 17,164

Debt

Debt	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Debt	Debt Debt, net of debt discount and issuance costs, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Senior Credit Facility $ — $ — Convertible Notes Facility 177,735 122,692 Total debt $ 177,735 $ 122,692 Less debt, current 177,735 122,692 Debt, non-current $ — $ — 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 9, 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 certain specified percentage of eligible accounts receivable and inventory, subject to certain reserves, to be determined in accordance with the Senior Credit Facility. The Senior Credit Facility includes a $25.0 million letter of credit sub-line as of March 31, 2023. 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 certain other excluded assets. Borrowings under the Senior Credit Facility bore 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. On April 3, 2023, the Company entered into the Third Amendment to the Senior Credit Facility to replace the references of LIBOR in the loan document with Term SOFR, a rate based on the secured overnight financing rate as administered by the Federal Reserve Bank of New York as disclosed in Note 11, Subsequent Events. There was no outstanding balance for borrowings under the Senior Credit Facility as of March 31, 2023 and December 31, 2022. There was an aggregate of $20.1 million in letters of credit outstanding under the Senior Credit Facility as of March 31, 2023. 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 Facility In August 2020, Legacy Proterra issued $200.0 million aggregate principal of Convertible Notes with an initial maturity date on August 4, 2025. The Convertible Notes had a cash interest of 5.0% per annum payable at each quarter end and a paid-in-kind (“PIK”) interest of 4.5% per annum payable by increasing the principal balance at each quarter end. 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. The Convertible Notes are secured by substantially all of the assets of Legacy Proterra, including its intellectual property. 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 Company may not make prepayment unless approved by the required holders of the Convertible Notes. 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 (“Minimum Liquidity Covenant”) 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. See below for details regarding modifications to the Minimum Liquidity Covenant. 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 capital stock at an exercise price of $0.02 per share. The warrants were 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 was reclassified to stockholders’ equity. In the fourth quarter of 2021, all remaining outstanding warrants were exercised. 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 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 qualified 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 volume-weighted average price (“VWAP”) of the common stock exceeds $9.86 over 20 consecutive days subsequent to January 13, 2022. The amortization expense of debt discount and issuance costs were $3.8 million and $3.3 million for the three months ended March 31, 2023 and 2022, respectively. The Company was not in compliance with the Minimum Liquidity Covenant of the Convertible Notes Facility as of December 31, 2022. The Company received a waiver of the Liquidity (as defined therein) requirement in February 2023 which provided for retroactive effect, so that no such event of default occurred in the year ended December 31, 2022. The audit report included in the Annual Report on Form 10-K (the “2022 Financials”) contained a going concern qualification. The Company’s inability to deliver audited financial statements certified by the Company’s independent registered public accounting firm without qualification (or similar notation) as to going concern is an event of default under both the Senior Credit Facility and the Convertible Notes Facility. On March 14, 2023, the Company obtained a limited advance waiver from the holders of the Convertible Notes with respect to the Going Concern Covenant until March 31, 2023. On March 31, 2023, the Company received a waiver for the Senior Credit Facility to consent to the delivery of the 2022 Financials with a going concern qualification and waived the cross default of the corresponding covenant under the Convertible Notes Facility in connection with the 2022 Financials. As a result, the Company was in compliance with the covenants contained in the Senior Credit Facility and Convertible Facility as of March 31, 2023. Amendment to the Convertible Notes Facility On March 31, 2023, the Company entered into an amendment to the Convertible Notes Facility, which includes amendments to the interest rate, maturity date, mandatory and optional conversion rights, limitations on the issuance of shares of the Company’s common stock upon conversion and the Company’s obligation to seek stockholder approvals as described below, minimum liquidity requirements and certain other covenants described in further detail below. Following such amendment on March 31, 2023, the Convertible Notes Facility provides for (i) a waiver of the Minimum Liquidity Covenant through May 31, 2024, requiring instead a minimum Liquidity of $125.0 million as of the last day of each quarter from March 31, 2023 through and including May 31, 2024, and (ii) a waiver of the requirement that the Company’s financial statements be certified by the Company’s auditor without qualification (or similar notation) as to going concern for the Company’s consolidated financial statements for fiscal years 2022 and 2023. After May 31, 2024, the Convertible Notes Facility requires the Company to maintain Liquidity at each 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. In addition, the Convertible Notes Facility contains an additional holding company covenant limiting the Company’s ability to engage in business, operations and activities other than as set forth in the Convertible Notes Facility. The Convertible Notes Facility extends the maturity date of the Convertible Notes to August 4, 2028, except with respect to $3.5 million original principal amount. The annual interest rate was increased to 12.0% per annum, consisting of 5.0% in cash and 7.0% PIK interest with the PIK default rate proportionally increased to 9.0%. The increased PIK interest on the Convertible Notes is to be accrued from March 17, 2023. Following the amendment on March 31, 2023, the Convertible Notes Facility amended the mandatory conversion provision in the existing Convertible Notes to provide for mandatory conversion only on or after March 31, 2024, if the daily VWAP of the Company’s common stock equals or exceeds (a) $15.00 after March 31, 2024 to but not including March 31, 2025, or (b) $12.00 after March 31, 2025, in each case, over a period of 20 consecutive trading days and providing that if the mandatory conversion trigger is met, to convert at a conversion price equal to (i) $4.00 until 1/3 of the aggregate balance of such Convertible Note (including all PIK interest and cash interest accrued but not paid) is converted, (ii) thereafter, $5.00 until 1/3 of the aggregate balance of the such Convertible Note is converted, and (iii) thereafter, $6.00. The conversion prices will be equitably adjusted to reflect any stock dividends, stock splits, reverse stock splits, recapitalizations or other similar events. In addition, following the amendment on March 31, 2023, under the terms of the Convertible Notes Facility, holders of the Convertible Notes shall have an additional option, at any time on or after March 31, 2024 until maturity of the Convertible Notes, to convert at a conversion price equal to (i) $4.00 until 1/3 of the aggregate balance of the such Convertible Note is converted, (ii) thereafter, $5.00 until 1/3 of the aggregate balance of the such Convertible Note is converted, and (iii) thereafter, $6.00, which conversion right shall be exercisable in whole or in part from time to time; provided, however, that if the Company consummates a Qualified Financing (as defined below), the holder, at its option, at any time or from time to time on or after March 31, 2024, may convert its Convertible Notes at a conversion price equal to 75% of the lowest per share cash purchase price of the common stock or preferred stock sold by Proterra in any Qualified Financing, subject to a $1.016 floor conversion price. “Qualified Financing” means, as of any date of determination, a bona fide equity financing, if any, on or after March 31, 2023, in which the Company or Proterra OpCo sells equity or equity-linked securities in a capital-raising transaction (which may include a public offering of the Company’s equity securities). Subject to certain exceptions, the Convertible Notes also restrict the Company’s ability to, among other things: dispose of or sell the Company’s assets; make material changes in the Company’s business or management, or accounting and reporting practices; acquire, consolidate, or merge with other entities; incur additional indebtedness; create liens on the Company’s assets; pay dividends; make investments; enter transactions with affiliates; and pre-pay other indebtedness. The Convertible Notes also contain customary events of default, including, among others, the failure to make any payment of principal (or any other payment) when due under the Convertible Notes within five The Convertible Notes Facility provides that no “person” or “group” (within the meaning of Section 13(d) of the Exchange Act) will be entitled to receive any of the Company’s common stock otherwise deliverable upon conversion of the Convertible Notes to the extent that such receipt would cause such person or group to become, directly or indirectly, a “beneficial owner” as defined in Rule 13d-3 under the Exchange Act of more than 40% of the Company’s common stock outstanding at such time (the “Beneficial Ownership Limitation”), and no conversion of the Convertible Notes shall take place to the extent (but only to the extent) that such receipt (or conversion) would cause any Note holder or its affiliates to beneficially own shares of the Company’s common stock in excess of the Beneficial Ownership Limitation. The Convertible Notes Facility also provides for certain limitations on the conversion rights of the holders of the Convertible Notes, including caps on the number of shares of common stock deliverable upon conversion subject to obtaining stockholder approval, as described below. The Company has agreed to use its best efforts to obtain stockholder approval of (i) the issuance of more than 19.99% of the Company’s outstanding common stock in accordance with Nasdaq listing standards (the “Nasdaq Proposal”) and (ii) an amendment to the Company’s certificate of incorporation to increase the number of authorized shares of common stock. Prior to the receipt of stockholder approval of the Nasdaq Proposal, the maximum number of shares of common stock that may be issued upon conversions of the Convertible Notes will be 45,257,360 shares. If stockholder approval of the Nasdaq Proposal is obtained, until and unless the Company receives stockholder approval of an amendment to the Company’s certificate of incorporation to increase the number of authorized shares of the Company’s common stock, the maximum number of shares of common stock that may be issued upon conversions of the Convertible Notes will be 177,782,000 shares. If the Company receives both stockholder approvals, the number of shares of the Company’s common stock that may be issued upon conversion of the Convertible Notes will be limited by the number of authorized and available shares, subject to the Beneficial Ownership Limitation described above. The Company is obligated to use best efforts to seek the above stockholder approvals as promptly as practicable and no later than the Company’s 2023 annual meeting of stockholders; provided that if such stockholder approvals are not received at the Company’s 2023 annual meeting of stockholders, the Company is obligated to call a special meeting of stockholders every 6 months until such stockholder approvals are received. For any additional shares exceeding the 45,257,360 or 177,782,000 share limits set forth above, the Convertible Notes holders have the right to elect either (x) to rescind the conversion with respect to (and only with respect to) the portion of the balance of the Convertible Notes that relates to the number of shares of the Company’s common stock exceeding the applicable limitations (the “Excess Shares”), or (y) for the Company to pay to such Convertible Note holder an amount equal to the product of (A) the number of Excess Shares, multiplied by (B) the simple average of the daily VWAP of the common stock for the 20 consecutive trading days ending on and including the trading day immediately preceding the applicable conversion date. Immediately prior to the amendment to the Convertible Notes Facility, the Convertible Notes, net of debt discount and issuance costs, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Principal $ 153,500 $ 153,500 PIK interest 19,196 17,301 Total principal 172,696 170,801 Less debt discount and issuance costs (44,275) (48,109) Total Convertible Notes $ 128,421 $ 122,692 In accordance with ASC Topic No. 470-50, Debt – Modifications and Extinguishments, the amendment to the Convertible Notes Facility on March 31, 2023 was determined to be an extinguishment of the existing debt and an issuance of new debt upon the effectiveness of the amendment to the Convertible Notes Facility on March 31, 2023 . The new debt is initially recorded at its fair value of $313.4 million, and a loss on debt extinguishment is calculated as the difference between the fair value of the new debt, the net carrying amount of the old debt, and other adjustments required under US GAAP. The Company recorded a loss on debt extinguishment of $177.9 million in the condensed consolidated statements of operations and the $7.2 million fair value of the mandatory conversion feature under the Convertible Notes immediately prior to the amendment to the Convertible Notes Facility were recorded to offset stockholders’ equity in accordance with Topic 815, Derivatives and Hedging. The embedded features in the Convertible Notes are composed of conversion options that had the economic characteristics of a contingent early redemption feature settled in a variable number of shares of the Company’s common stock. These conversion options were bifurcated and accounted for as a derivative liability separately from the host debt instrument. As of March 31, 2023, the fair value of derivative liability of $135.7 million was recorded as debt discount on the condensed consolidated balance sheets, which will be amortized during the term of the Convertible Notes to interest expense using the effective-interest method. The derivative liability will be remeasured on a recurring basis at each reporting period date, with the change in fair value reported in the statement of operations. Upon effectiveness of the amendment to the Convertible Notes Facility as of March 31, 2023, the Convertible Notes, inclusive of debt premium, consisted of the following (in thousands): March 31, 2023 Principal $ 153,500 PIK interest 19,371 Total principal 172,871 Plus debt premium 4,864 Total Convertible Notes $ 177,735 As of March 31, 2023, the contractual future principal repayments of the total debt were as follows (in thousands): 2023 $ — 2025 (1) 3,941 2028 (1) 168,930 Total debt $ 172,871 __________________ (1) Including PIK interest added to principal balance through March 31, 2023. Based on the current price of the Company’s common stock, the holders of Convertible Notes could potentially have the right to elect cash payment for any Excess Shares upon conversion as early as March 31, 2024 if the Company were to complete a Qualified Financing transaction. As a result, even though the Convertible Notes have a maturity date beyond 12 months from March 31, 2023, the related liabilities were classified as current liability on the Company’s condensed consolidated balance sheets as of March 31, 2023.

Leases

Leases	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Leases	Leases As a Lessor The net investment in leases were as follows (in thousands): March 31, 2023 December 31, 2022 Net investment in leases, current $ 872 $ 985 Net investment in leases, non-current 9,173 9,304 Total net investment in leases $ 10,045 $ 10,289 Interest income from accretion of net investment in lease was not material in the three months ended March 31, 2023 or 2022. Future minimum payments receivable from operating and sales-type leases as of March 31, 2023 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2023 $ 279 $ 580 2024 — 1,010 2025 — 1,528 2026 — 1,528 2027 — 1,528 Thereafter — 4,013 Total minimum lease payments $ 279 $ 10,187 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 finance leases as of March 31, 2023. Maturities of operating lease liabilities as of March 31, 2023 were as follows (in thousands): Remainder of 2023 $ 6,122 2024 4,224 2025 3,487 2026 2,615 2027 2,238 Thereafter 9,858 Total undiscounted lease payment 28,544 Less: imputed interest (5,305) Total operating lease liabilities $ 23,239 Operating lease expense was $2.1 million and $1.5 million for the three months ended March 31, 2023 and 2022, respectively. Short-term and variable lease expenses for the three months ended March 31, 2023 and 2022 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Three Months Ended March 31, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (2,082) $ (1,377) Lease liabilities arising from obtaining right-of-use assets: Operating lease $ — $ 25 Finance lease 699 — Operating lease right-of-use assets and liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Operating leases Operating lease right-of-use assets $ 18,661 $ 20,274 Operating lease liabilities, current 5,998 6,876 Operating lease liabilities, non-current 17,241 18,098 Total operating lease liabilities $ 23,239 $ 24,974 The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.1%, respectively, as of March 31, 2023. The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.2%, respectively, as of December 31, 2022. As of March 31, 2023, 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): March 31, 2023 December 31, 2022 Net investment in leases, current $ 872 $ 985 Net investment in leases, non-current 9,173 9,304 Total net investment in leases $ 10,045 $ 10,289 Interest income from accretion of net investment in lease was not material in the three months ended March 31, 2023 or 2022. Future minimum payments receivable from operating and sales-type leases as of March 31, 2023 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2023 $ 279 $ 580 2024 — 1,010 2025 — 1,528 2026 — 1,528 2027 — 1,528 Thereafter — 4,013 Total minimum lease payments $ 279 $ 10,187 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 finance leases as of March 31, 2023. Maturities of operating lease liabilities as of March 31, 2023 were as follows (in thousands): Remainder of 2023 $ 6,122 2024 4,224 2025 3,487 2026 2,615 2027 2,238 Thereafter 9,858 Total undiscounted lease payment 28,544 Less: imputed interest (5,305) Total operating lease liabilities $ 23,239 Operating lease expense was $2.1 million and $1.5 million for the three months ended March 31, 2023 and 2022, respectively. Short-term and variable lease expenses for the three months ended March 31, 2023 and 2022 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Three Months Ended March 31, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (2,082) $ (1,377) Lease liabilities arising from obtaining right-of-use assets: Operating lease $ — $ 25 Finance lease 699 — Operating lease right-of-use assets and liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Operating leases Operating lease right-of-use assets $ 18,661 $ 20,274 Operating lease liabilities, current 5,998 6,876 Operating lease liabilities, non-current 17,241 18,098 Total operating lease liabilities $ 23,239 $ 24,974 The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.1%, respectively, as of March 31, 2023. The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.2%, respectively, as of December 31, 2022. As of March 31, 2023, 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): March 31, 2023 December 31, 2022 Net investment in leases, current $ 872 $ 985 Net investment in leases, non-current 9,173 9,304 Total net investment in leases $ 10,045 $ 10,289 Interest income from accretion of net investment in lease was not material in the three months ended March 31, 2023 or 2022. Future minimum payments receivable from operating and sales-type leases as of March 31, 2023 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2023 $ 279 $ 580 2024 — 1,010 2025 — 1,528 2026 — 1,528 2027 — 1,528 Thereafter — 4,013 Total minimum lease payments $ 279 $ 10,187 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 finance leases as of March 31, 2023. Maturities of operating lease liabilities as of March 31, 2023 were as follows (in thousands): Remainder of 2023 $ 6,122 2024 4,224 2025 3,487 2026 2,615 2027 2,238 Thereafter 9,858 Total undiscounted lease payment 28,544 Less: imputed interest (5,305) Total operating lease liabilities $ 23,239 Operating lease expense was $2.1 million and $1.5 million for the three months ended March 31, 2023 and 2022, respectively. Short-term and variable lease expenses for the three months ended March 31, 2023 and 2022 were not material. Supplemental cash flow information related to leases were as follows (in thousands): Three Months Ended March 31, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (2,082) $ (1,377) Lease liabilities arising from obtaining right-of-use assets: Operating lease $ — $ 25 Finance lease 699 — Operating lease right-of-use assets and liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Operating leases Operating lease right-of-use assets $ 18,661 $ 20,274 Operating lease liabilities, current 5,998 6,876 Operating lease liabilities, non-current 17,241 18,098 Total operating lease liabilities $ 23,239 $ 24,974 The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.1%, respectively, as of March 31, 2023. The weighted average remaining lease term and discount rate of operating leases were 6.4 years and 6.2%, respectively, as of December 31, 2022. As of March 31, 2023, the Company had no significant additional operating leases and finance leases that have not yet commenced.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments As of March 31, 2023, the Company had outstanding inventory and other purchase commitments of $2.1 billion. Most of the commitments relate to the expected purchase of cylindrical cells to be 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 March 31, 2023, the Company has made a $10.0 million prepayment, which was recorded as the long-term inventory prepayment on the consolidated balance sheets. The Company expects the 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 March 31, 2023, the Company had letters of credit outstanding totaling $20.2 million, which will expire over various dates in 2023 and 2024. 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	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Stockholders' Equity	Stockholders’ EquityThe 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 March 31, 2023, 226,852,590 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. As of March 31, 2023, the Company had reserved shares of common stock for issuance as follows (in thousands): 2010 Equity Incentive Plan 16,331 2021 Equity Incentive Plan 29,251 2021 Employee Stock Purchase Plan 5,463 Warrants 1 Earnout Stock 18,009 Convertible notes 45,257 Total 114,312

Equity Plans and Stock-based Co

Equity Plans and Stock-based Compensation	3 Months Ended
	Mar. 31, 2023
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 March 31, 2023, options to purchase 16,331,367 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 and 2023, the shares of common stock reserved for issuance were increased by 8,878,388 and 9,050,606, respectively, pursuant to the 2021 Plan. The exercise price of stock options granted must be at least equal to the fair market value of common stock on the date of grant. Incentive stock options granted to an individual who holds, directly or by attribution, more than ten percent of the total combined voting power of all classes of capital stock must have an exercise price of at least 110% of the fair market value of common stock on the date of grant. Subject to certain adjustments, no more than 30,000,000 shares may be issued pursuant to the exercise of incentive stock options granted under the 2021 Plan. The maximum term of options granted is ten years from the date of grant, except that the maximum permitted term of incentive stock options granted to an individual who holds, directly or by attribution, more than ten percent of the total combined voting power of all classes of capital stock is five years from the date of grant. 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 and 2023, the shares of common stock reserved for issuance were increased by 2,219,597 and 2,262,651, respectively, pursuant to the ESPP. 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 $0.3 million of stock-based compensation expense for the three months ended March 31, 2023 and 2022, respectively. 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, 2022 (1) 14,256,697 4.32 5.5 $ 9,469 Granted 2,075,398 1.50 Exercised (57,036) 1.98 Cancelled/forfeited/expired (362,967) 6.67 Balance as of March 31, 2023 (1) 15,912,092 3.91 5.6 $ 372 Exercisable as of March 31, 2023 (2) 12,216,812 3.96 4.5 $ 331 __________________ (1) Excluding Equity Awards of 2,677,500 shares and Milestone Options of 669,375 shares. See below for further details. (2) Excluding 2,008,124 shares exercisable under the Equity Awards with weighted average exercise price of $19.61 per share as of March 31, 2023. 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 $0.1 million for the three months ended March 31, 2023. The total estimated grant date fair value of stock options vested was $2.4 million for the three months ended March 31, 2023. As of March 31, 2023, the total unrecognized stock-based compensation expense related to outstanding stock options was $11.7 million, which is expected to be recognized over a weighted-average period of 2.6 years. The fair value of stock options granted is estimated on the date of grant using the following assumptions: Three Months Ended March 31, 2023 2022 Expected term (in years) 6.3 6.1 Risk-free interest rate 3.6 % 1.9 % Expected volatility 55.1 % 55.0 % 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 Balance as of December 31, 2022 5,733,227 $ 7.07 Granted 3,825,133 1.75 Released (530,393) 7.17 Forfeited (521,679) 7.72 Balance as of March 31, 2023 8,506,288 $ 4.63 The compensation expense related to the service-based RSU awards is determined using the fair market value of the Company’s common stock on the date of the grant. As of March 31, 2023, the total unrecognized stock-based compensation expense related to outstanding RSUs was $34.2 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 March 31, 2023 2022 Cost of goods sold $ 305 $ 516 Research and development 1,192 993 Selling, general and administrative 2,817 3,133 Total stock-based compensation expense $ 4,314 $ 4,642

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	Net 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 loss per share of common stock attributable to common stockholders was as follows (in thousands, except for per share data): Three Months Ended March 31, 2023 2022 Numerator: Net loss $ (243,977) $ (50,078) Effect of dilutive securities: Interest expense to be recognized upon conversion of Convertible Notes (1) — (55,185) Numerator for diluted EPS - Net loss after the effect of dilutive securities $ (243,977) $ (105,263) Denominator: Weighted-average shares used in computing net loss per share of common stock, basic 226,410 222,276 Convertible Notes (1) — 24,855 Diluted weighted average shares 226,410 247,131 Net loss per share of common stock: Basic $ (1.08) $ (0.23) Diluted $ (1.08) $ (0.43) __________________ (1) Adjustment is under the “if-converted” method. Adjustments for the three months ended March 31, 2022 include write-off of $62.3 million unamortized debt discount of the Convertible Notes as of December 31, 2021, offset by the $7.1 million interest expense recorded in net loss of three months ended March 31, 2022. 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. Prior to the amendment to the Convertible Notes Facility, the outstanding Convertible Notes including accrued interest would have been 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. As of March 31, 2023, the conditions for the convertible features under the Convertible Notes Facility were not satisfied. See Note 4, Debt, for additional information on the conversion provisions of the Convertible Notes. Since the Company was in a loss position after the effect of diluted 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): March 31, 2023 Stock options and RSUs to purchase common stock 27,765 Warrants to purchase common stock 1 Convertible notes (2) 35,535 Total 63,301 __________________

401(k) Plan

401(k) Plan	3 Months Ended
	Mar. 31, 2023
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 $1.1 million and $0.7 million in the three months ended March 31, 2023 and 2022, respectively.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In April 2023, the Company entered into the Third Amendment to the Senior Credit Facility to replace the references of LIBOR in the loan document with Term SOFR, a rate based on the secured overnight financing rate as administered by the Federal Reserve Bank of New York.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
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”). 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, 2022 and the related notes incorporated by reference in the Company’s Annual Report (the “Annual Report”) on Form 10-K, filed with SEC on March 17, 2023 and amended on May 1, 2023, which provides a more complete discussion of the Company’s accounting policies and certain other information. The information as of December 31, 2022 and 2021 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 March 31, 2023 and the results of operations and cash flows for the three months ended March 31, 2023 and 2022. The results of operations for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the year ending December 31, 2023.
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 Türkiye.The Company’s chief operating decision maker is its Chief Executive Officer (CEO) who reviews financial information presented on a consolidated basis for purposes of making decision on allocating resources and assessing financial performance. 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 March 31, 2023 and December 31, 2022.
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 March 31, 2023, 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 Türkiye. 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 March 31, March 31, December 31, 2023 2022 2023 2022 Number of customers accounted for 10% or more 3 2 4 2 Total % for customers accounted for 10% or more 34% 40% 49% 48% Single source suppliers provide the Company with a number of components that are required for manufacturing of its current products. For example, we sole source our composite bus bodies from TPI Composites Inc. 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, 2022 $ 67,398 Revenue recognized from beginning balance during the three months ended March 31, 2023 (6,815) Deferred revenue added during the three months ended March 31, 2023 24,812 Deferred revenue as of March 31, 2023 $ 85,395 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 $0.3 million and $0.3 million in the three months ended March 31, 2023 and 2022, 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 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 $1.2 million and $2.1 million for the three months ended March 31, 2023 and 2022, respectively. Extended warranty revenue was $0.6 million and $0.4 million for the three months ended March 31, 2023 and 2022, respectively. As of March 31, 2023 and December 31, 2022, the contract assets balance was $13.0 million and $26.1 million, respectively, and are recorded in the prepaid expenses and other current assets on the consolidated balance sheets. The contract assets are expected to be billed within the next twelve months. As of March 31, 2023, the amount of remaining performance obligations that have not been recognized as revenue was $472.9 million, of which 68% 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 has the following commercial offerings each addressing a critical component of commercial vehicle electrification. • 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 offers turnkey fleet-scale, high-power charging solutions and
Product Warranties	Product WarrantiesWarranty expense is recorded as a component of cost of goods sold.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2023
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 March 31, 2023 2022 United States $ 65,424 $ 51,967 Rest of World 14,105 6,614 $ 79,529 $ 58,581
Concentration of Customer Risk	Revenue Accounts Receivable Three Months Ended March 31, March 31, December 31, 2023 2022 2023 2022 Number of customers accounted for 10% or more 3 2 4 2 Total % for customers accounted for 10% or more 34% 40% 49% 48%
Deferred Revenue	The changes in deferred revenue consisted of the following (in thousands): Deferred revenue as of December 31, 2022 $ 67,398 Revenue recognized from beginning balance during the three months ended March 31, 2023 (6,815) Deferred revenue added during the three months ended March 31, 2023 24,812 Deferred revenue as of March 31, 2023 $ 85,395
Revenue of Commercial Offerings	Revenue of these commercial offerings are as follows (in thousands): Three Months Ended March 31, 2023 2022 Proterra Transit $ 44,862 $ 35,381 Proterra Powered & Energy 34,667 23,200 Total $ 79,529 $ 58,581
Accrued Warranty Activity	Accrued warranty activity consisted of the following (in thousands): Three Months Ended March 31, 2023 Warranty reserve - beginning of period $ 25,513 Warranty costs incurred (868) Net changes in liability for pre-existing warranties, including expirations — Provision for warranty 3,604 Warranty reserve - end of period $ 28,249

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis using the above input categories were as follows (in thousands): Pricing Category Fair Value at March 31, 2023 December 31, 2022 Assets: Cash equivalents and marketable securities: Money market funds Level 1 $ 57,325 $ 14,941 U.S. Treasury securities Level 1 74,689 — Short-term investments: U.S. Treasury securities Level 1 128,341 224,359 Total $ 260,355 $ 239,300 Liabilities: Other non-current liabilities Derivative liability Level 3 $ 135,678 $ — Total $ 135,678 $ —
Summary of Cash Equivalents and Marketable Securities	The following is a summary of cash equivalents and marketable securities as of March 31, 2023 (in thousands): Amortized Cost Unrealized Gain Estimated Fair Value Cash equivalents: Money market funds $ 57,325 $ — $ 57,325 U.S. Treasury securities 74,689 — 74,689 Short-term investments: U.S. Treasury securities 128,278 63 128,341 Total $ 260,292 $ 63 $ 260,355 The following is a summary of cash equivalents and marketable securities as of December 31, 2022 (in thousands): Amortized Cost Unrealized Loss Estimated Fair Value Cash equivalents: Money market funds $ 14,941 $ — $ 14,941 Short-term investments: U.S. Treasury securities 224,904 (545) 224,359 Total $ 239,845 $ (545) $ 239,300

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents	Cash and cash equivalents consisted of the following (in thousands): March 31, 2023 December 31, 2022 Cash $ 35,891 $ 58,754 Cash equivalents 132,014 14,941 Total cash and cash equivalents $ 167,905 $ 73,695 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. March 31, 2023 December 31, 2022 Cash and cash equivalents $ 167,905 $ 73,695 Restricted cash, current portion 12,565 12,565 Total cash and cash equivalents, and restricted cash $ 180,470 $ 86,260
Inventories	Inventories consisted of the following (in thousands): March 31, 2023 December 31, 2022 Raw materials $ 163,327 $ 127,199 Work in progress 22,419 21,153 Finished goods 11,123 13,518 Service parts 8,620 7,697 Total inventories $ 205,489 $ 169,567
Property, Plant and Equipment, Net	Property, plant, and equipment, net, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Computer hardware $ 6,020 $ 5,465 Computer software 12,813 11,012 Internally used vehicles and charging systems 15,177 15,177 Leased vehicles and batteries 5,142 5,142 Leasehold improvements 30,883 10,716 Machinery and equipment 54,195 28,942 Office furniture and equipment 3,282 2,523 Tooling 23,971 22,430 Finance lease right-of-use assets 878 179 Construction in progress 29,209 72,505 181,570 174,091 Less: Accumulated depreciation and amortization (71,145) (66,539) Total $ 110,425 $ 107,552
Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Accrued payroll and related expenses $ 6,493 $ 8,647 Accrued sales and use tax 1,284 1,784 Warranty reserve 8,229 8,406 Accrued supplier liability 4,059 7,699 Insurance related 1,764 4,445 Other accrued expenses 3,433 2,570 Total $ 25,262 $ 33,551
Other Long-Term Liabilities	Other long-term liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Warranty reserve $ 20,020 $ 17,107 Finance lease liabilities, non-current 512 57 Total $ 20,532 $ 17,164

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Debt Components	Debt, net of debt discount and issuance costs, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Senior Credit Facility $ — $ — Convertible Notes Facility 177,735 122,692 Total debt $ 177,735 $ 122,692 Less debt, current 177,735 122,692 Debt, non-current $ — $ —
Convertible Notes and Amended Notes	Immediately prior to the amendment to the Convertible Notes Facility, the Convertible Notes, net of debt discount and issuance costs, consisted of the following (in thousands): March 31, 2023 December 31, 2022 Principal $ 153,500 $ 153,500 PIK interest 19,196 17,301 Total principal 172,696 170,801 Less debt discount and issuance costs (44,275) (48,109) Total Convertible Notes $ 128,421 $ 122,692 Upon effectiveness of the amendment to the Convertible Notes Facility as of March 31, 2023, the Convertible Notes, inclusive of debt premium, consisted of the following (in thousands): March 31, 2023 Principal $ 153,500 PIK interest 19,371 Total principal 172,871 Plus debt premium 4,864 Total Convertible Notes $ 177,735
Contractual Future Principal Repayments of Debt	As of March 31, 2023, the contractual future principal repayments of the total debt were as follows (in thousands): 2023 $ — 2025 (1) 3,941 2028 (1) 168,930 Total debt $ 172,871 __________________

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Net Investment in Leases	The net investment in leases were as follows (in thousands): March 31, 2023 December 31, 2022 Net investment in leases, current $ 872 $ 985 Net investment in leases, non-current 9,173 9,304 Total net investment in leases $ 10,045 $ 10,289
Future Minimum Payments Receivable from Operating Leases	Future minimum payments receivable from operating and sales-type leases as of March 31, 2023 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2023 $ 279 $ 580 2024 — 1,010 2025 — 1,528 2026 — 1,528 2027 — 1,528 Thereafter — 4,013 Total minimum lease payments $ 279 $ 10,187
Future Minimum Payments Receivable from Sales-Type Leases	Future minimum payments receivable from operating and sales-type leases as of March 31, 2023 for each of the next five years were as follows: Operating leases Sales-type leases Remainder of 2023 $ 279 $ 580 2024 — 1,010 2025 — 1,528 2026 — 1,528 2027 — 1,528 Thereafter — 4,013 Total minimum lease payments $ 279 $ 10,187
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of March 31, 2023 were as follows (in thousands): Remainder of 2023 $ 6,122 2024 4,224 2025 3,487 2026 2,615 2027 2,238 Thereafter 9,858 Total undiscounted lease payment 28,544 Less: imputed interest (5,305) Total operating lease liabilities $ 23,239
Supplemental Cash Flow Information	Supplemental cash flow information related to leases were as follows (in thousands): Three Months Ended March 31, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ (2,082) $ (1,377) Lease liabilities arising from obtaining right-of-use assets: Operating lease $ — $ 25 Finance lease 699 —
Operating Lease Right-Of-Use Assets and Liabilities	Operating lease right-of-use assets and liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Operating leases Operating lease right-of-use assets $ 18,661 $ 20,274 Operating lease liabilities, current 5,998 6,876 Operating lease liabilities, non-current 17,241 18,098 Total operating lease liabilities $ 23,239 $ 24,974

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Reserved Shares of Common Stock	As of March 31, 2023, the Company had reserved shares of common stock for issuance as follows (in thousands): 2010 Equity Incentive Plan 16,331 2021 Equity Incentive Plan 29,251 2021 Employee Stock Purchase Plan 5,463 Warrants 1 Earnout Stock 18,009 Convertible notes 45,257 Total 114,312

Equity Plans and Stock-based _2

Equity Plans and Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2022 (1) 14,256,697 4.32 5.5 $ 9,469 Granted 2,075,398 1.50 Exercised (57,036) 1.98 Cancelled/forfeited/expired (362,967) 6.67 Balance as of March 31, 2023 (1) 15,912,092 3.91 5.6 $ 372 Exercisable as of March 31, 2023 (2) 12,216,812 3.96 4.5 $ 331 __________________ (1) Excluding Equity Awards of 2,677,500 shares and Milestone Options of 669,375 shares. See below for further details. (2) Excluding 2,008,124 shares exercisable under the Equity Awards with weighted average exercise price of $19.61 per share as of March 31, 2023.
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: Three Months Ended March 31, 2023 2022 Expected term (in years) 6.3 6.1 Risk-free interest rate 3.6 % 1.9 % Expected volatility 55.1 % 55.0 % 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 Balance as of December 31, 2022 5,733,227 $ 7.07 Granted 3,825,133 1.75 Released (530,393) 7.17 Forfeited (521,679) 7.72 Balance as of March 31, 2023 8,506,288 $ 4.63
Stock-Based Compensation Expense	Stock-based compensation expense included in operating results was as follows (in thousands): Three Months Ended March 31, 2023 2022 Cost of goods sold $ 305 $ 516 Research and development 1,192 993 Selling, general and administrative 2,817 3,133 Total stock-based compensation expense $ 4,314 $ 4,642

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The computation of basic and diluted net loss per share of common stock attributable to common stockholders was as follows (in thousands, except for per share data): Three Months Ended March 31, 2023 2022 Numerator: Net loss $ (243,977) $ (50,078) Effect of dilutive securities: Interest expense to be recognized upon conversion of Convertible Notes (1) — (55,185) Numerator for diluted EPS - Net loss after the effect of dilutive securities $ (243,977) $ (105,263) Denominator: Weighted-average shares used in computing net loss per share of common stock, basic 226,410 222,276 Convertible Notes (1) — 24,855 Diluted weighted average shares 226,410 247,131 Net loss per share of common stock: Basic $ (1.08) $ (0.23) Diluted $ (1.08) $ (0.43) __________________ (1) Adjustment is under the “if-converted” method. Adjustments for the three months ended March 31, 2022 include write-off of $62.3 million unamortized debt discount of the Convertible Notes as of December 31, 2021, offset by the $7.1 million interest expense recorded in net loss of three months ended March 31, 2022.
Potentially Dilutive Securities Excluded from the Diluted Per Share Calculation	The potentially dilutive securities were as follows (in thousands): March 31, 2023 Stock options and RSUs to purchase common stock 27,765 Warrants to purchase common stock 1 Convertible notes (2) 35,535 Total 63,301 __________________

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)		3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2023 USD ($) segment	Mar. 31, 2022 USD ($)	May 31, 2024 USD ($)	Mar. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)		Aug. 31, 2020 USD ($)
Accounting Policies [Abstract]
Accumulated deficit	$ (1,340,152,000)	$ (1,340,152,000)				$ (1,096,175,000)	[1]
Cash and cash equivalents and short-term investments	296,200,000	296,200,000
Debt Instrument [Line Items]
Outstanding balance	177,735,000	177,735,000				122,692,000
Loss on debt extinguishment		177,939,000	$ 0
Impairment charge		$ 0	$ 0
Number of reportable segments | segment		1
Line of credit | Senior Credit Facility
Debt Instrument [Line Items]
Outstanding balance	0	$ 0				0
Letters of credit outstanding, amount	20,200,000	20,200,000
Convertible debt | Convertible Notes
Debt Instrument [Line Items]
Outstanding balance					$ 128,421,000	122,692,000
Total principal					172,696,000	170,801,000
PIK interest					$ 19,196,000	17,301,000
Covenant, required minimum liquidity								$ 75,000,000
Covenant, required minimum liquidity, multiple factor of cash burn								4
Loss on debt extinguishment	177,900,000
Convertible debt | Convertible Notes Facility
Debt Instrument [Line Items]
Outstanding balance	177,735,000	177,735,000				$ 122,692,000
Total principal	172,871,000	172,871,000
PIK interest	19,371,000	19,371,000
Covenant, required minimum liquidity	125,000,000	125,000,000
Fair value of embedded derivative liability	$ 135,700,000	$ 135,700,000
Convertible debt | Convertible Notes Facility | Forecast
Debt Instrument [Line Items]
Covenant, required minimum liquidity				$ 75,000,000
Covenant, required minimum liquidity, multiple factor of cash burn				4
[1]Derived from audited Consolidated Financial Statements.

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Revenue Disaggregated by Geography (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenue	$ 79,529	$ 58,581
United States
Disaggregation of Revenue [Line Items]
Total revenue	65,424	51,967
Rest of World
Disaggregation of Revenue [Line Items]
Total revenue	$ 14,105	$ 6,614

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Credit Risk and Concentration (Details) - Customer Concentration Risk - customer	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Revenue
Concentration Risk [Line Items]
Number of customers accounted for 10% or more	3	2
Revenue | Customers Accounted For Greater Than 10%
Concentration Risk [Line Items]
Concentration risk percentage	34%	40%
Accounts Receivable
Concentration Risk [Line Items]
Number of customers accounted for 10% or more	4		2
Accounts Receivable | Customers Accounted For Greater Than 10%
Concentration Risk [Line Items]
Concentration risk percentage	49%		48%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Deferred Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Change In Contract With Customer, Asset and Liability [Roll Forward]
Deferred revenue	$ 67,398
Revenue recognized from beginning balance during the three months ended March 31, 2023	(6,815)
Deferred revenue added during the three months ended March 31, 2023	24,812
Deferred revenue	$ 85,395

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Leasing revenue	$ 300	$ 300
Total revenue	79,529	58,581
Contract assets	13,000		$ 26,100
Remaining performance obligation	$ 472,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Disaggregation of Revenue [Line Items]
Remaining performance obligation, percentage	68%
Remaining performance obligation, term	12 months
Charging systems and installation
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,200	2,100
Extended warranty
Disaggregation of Revenue [Line Items]
Total revenue	$ 600	$ 400

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Revenue of Commercial Offerings (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenue	$ 79,529	$ 58,581
Proterra Transit
Disaggregation of Revenue [Line Items]
Total revenue	44,862	35,381
Proterra Powered & Energy
Disaggregation of Revenue [Line Items]
Total revenue	$ 34,667	$ 23,200

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Product Warranties (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty reserve - beginning of period	$ 25,513
Warranty costs incurred	(868)
Net changes in liability for pre-existing warranties, including expirations	0
Provision for warranty	3,604
Warranty reserve - end of period	$ 28,249

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Assets:
Total	$ 260,355	$ 239,300
Liabilities:
Total	135,678	0
Level 1 | U.S. Treasury securities
Assets:
Short-term investments	128,341	224,359
Level 1 | Money market funds
Assets:
Cash equivalents and marketable securities	57,325	14,941
Level 1 | U.S. Treasury securities
Assets:
Cash equivalents and marketable securities	74,689	0
Level 3
Liabilities:
Derivative liability	$ 135,678	$ 0

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	$ 132,014	$ 14,941
Unrealized Gain (Loss)	63	(545)
Amortized Cost	260,292	239,845
Estimated Fair Value	260,355	239,300
Cash equivalents: | Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	57,325	14,941
Cash equivalents: | U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Cash equivalents	74,689
Short-term investments: | U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	128,278	224,904
Unrealized Gain (Loss)	63	(545)
Estimated Fair Value	$ 128,341	$ 224,359

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2022	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Long-term investments		$ 26.6
Equity investment	$ 25

Balance Sheet Components - Cash

Balance Sheet Components - Cash and Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022		Mar. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents
Cash	$ 35,891	$ 58,754
Cash equivalents	132,014	14,941
Total cash and cash equivalents	167,905	73,695	[1]
Cash, Cash Equivalents, and Restricted Cash
Cash and cash equivalents	167,905	73,695	[1]
Restricted cash, current portion	12,565	12,565	[1]
Total cash and cash equivalents, and restricted cash	$ 180,470	$ 86,260		$ 59,929	$ 182,604
[1]Derived from audited Consolidated Financial Statements.

Balance Sheet Components - Inve

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 163,327	$ 127,199
Work in progress	22,419	21,153
Finished goods	11,123	13,518
Service parts	8,620	7,697
Total inventories	205,489	$ 169,567	[1]
Write-down of inventories	$ 0
[1]Derived from audited Consolidated Financial Statements.

Balance Sheet Components - Prop

Balance Sheet Components - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Finance lease right-of-use assets	$ 878		$ 179
Property, plant and equipment, and finance lease right-of-use asset gross	181,570		174,091
Less: Accumulated depreciation and amortization	(71,145)		(66,539)
Total	110,425		107,552	[1]
Depreciation and amortization expense	4,717	$ 3,381
Computer hardware
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,020		5,465
Computer software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	12,813		11,012
Internally used vehicles and charging systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	15,177		15,177
Leased vehicles and batteries
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,142		5,142
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	30,883		10,716
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	54,195		28,942
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	3,282		2,523
Tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23,971		22,430
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 29,209		$ 72,505
[1]Derived from audited Consolidated Financial Statements.

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related expenses	$ 6,493	$ 8,647
Accrued sales and use tax	1,284	1,784
Warranty reserve	8,229	8,406
Accrued supplier liability	4,059	7,699
Insurance related	1,764	4,445
Other accrued expenses	3,433	2,570
Total	$ 25,262	$ 33,551	[1]
[1]Derived from audited Consolidated Financial Statements.

Balance Sheet Components - Othe

Balance Sheet Components - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Warranty reserve	$ 20,020	$ 17,107
Finance lease liabilities, non-current	512	57
Total	$ 20,532	$ 17,164	[1]
[1]Derived from audited Consolidated Financial Statements.

Debt - Components (Details)

Debt - Components (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Total debt	$ 177,735	$ 122,692
Less debt, current	177,735	122,692	[1]
Debt, non-current	0	0
Line of credit | Senior Credit Facility
Debt Instrument [Line Items]
Total debt	0	0
Convertible debt | Convertible Notes Facility
Debt Instrument [Line Items]
Total debt	$ 177,735	$ 122,692
[1]Derived from audited Consolidated Financial Statements.

Debt - Senior Credit Facility (

Debt - Senior Credit Facility (Details) - USD ($)	1 Months Ended	3 Months Ended
	May 31, 2019	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Debt Instrument [Line Items]
Amount outstanding		$ 177,735,000		$ 122,692,000
Gain on debt extinguishment		(177,939,000)	$ 0
Line of credit | Senior Credit Facility
Debt Instrument [Line Items]
Amount outstanding		0		0
Letters of credit outstanding, amount		20,200,000
Line of credit | 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		$ 20,100,000
Line of credit | Federal Funds Rate | Variable rate component one | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	0.50%
Line of credit | London Interbank Offered Rate (LIBOR) | Variable rate component one | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	1%
Line of credit | London Interbank Offered Rate (LIBOR) | Minimum | Variable rate component two | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	1.50%
Line of credit | London Interbank Offered Rate (LIBOR) | Maximum | Variable rate component two | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	3%
Line of credit | Base Rate | Minimum | Variable rate component two | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	0%
Line of credit | Base Rate | Maximum | Variable rate component two | Senior Credit Facility
Debt Instrument [Line Items]
Spread on variable interest rate	1.50%
Letter of credit | Senior Credit Facility
Debt Instrument [Line Items]
Borrowing capacity	$ 25,000,000

Debt - Small Business Administr

Debt - Small Business Administration Loan (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	May 31, 2022	May 31, 2020	Mar. 31, 2023	Mar. 31, 2022
Debt Instrument [Line Items]
Gain on debt extinguishment			$ (177,939)	$ 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 and Fa

Debt - Convertible Notes and Facility and Amended Convertible Notes (Details)			3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares	Jun. 14, 2021 USD ($)	Mar. 31, 2023 USD ($) $ / shares shares	Mar. 31, 2022 USD ($)	May 31, 2024 USD ($)	Mar. 30, 2023 USD ($) shares	Dec. 31, 2022 USD ($)	Aug. 31, 2020 USD ($) $ / shares shares
Debt Instrument [Line Items]
Amortization of debt issuance cost and debt discounts			$ 3,854,000	$ 3,337,000
Special meeting of stockholders, period	6 months
Convertible Debt [Abstract]
Total debt	$ 177,735,000		177,735,000				$ 122,692,000
Loss on debt extinguishment			177,939,000	0
Debt extinguishment fair value adjustment			7,200,000
Additional Paid-in Capital
Convertible Debt [Abstract]
Debt extinguishment fair value adjustment			$ 7,200,000
Convertible note warrants
Debt Instrument [Line Items]
Warrant to purchase shares of convertible preferred stock (in shares) | shares								4,600,000
Fair value of embedded derivative liability								$ 68,500,000
Convertible note warrants | Convertible Notes
Debt Instrument [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares								$ 0.02
Warrant liability								$ 29,000,000
Convertible debt
Debt Instrument [Line Items]
Write off of unamortized debt issuance cost				62,300,000
Convertible debt | 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
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) | $ / shares	$ 6.5712		$ 6.5712
VWAP (in usd per share) | $ / shares	$ 9.86		$ 9.86
Consecutive days			20 days
Amortization of debt issuance cost and debt discounts			$ 3,800,000	$ 3,300,000
Covenant, required minimum liquidity, multiple factor of cash burn								4
Convertible Debt [Abstract]
Principal						$ 153,500,000	153,500,000
PIK interest						19,196,000	17,301,000
Total principal						172,696,000	170,801,000
Less debt discount and issuance costs/plus debt premium						(44,275,000)	(48,109,000)
Total debt						$ 128,421,000	122,692,000
Loss on debt extinguishment	$ 177,900,000
Debt extinguishment fair value adjustment			$ 7,200,000
Convertible debt | Convertible Notes Facility
Debt Instrument [Line Items]
Interest rate	12%		12%
Paid-in-kind interest rate	7%		7%
Covenant, required minimum liquidity	$ 125,000,000		$ 125,000,000
Fair value of embedded derivative liability	$ 135,700,000		135,700,000
Consecutive days	20 days
Face amount, maturity date not extended	$ 3,500,000		$ 3,500,000
Cash interest rate	5%		5%
PIK default rate	9%		9%
Conversion price discount percentage	75%		75%
Conversion price floor (in usd per share) | $ / shares	$ 1.016		$ 1.016
Breach of minimum liquidity covenant, period	5 days
Beneficial ownership limitation percentage	40%		40%
Maximum shares to be issued, percentage	19.99%		19.99%
Share cap | shares	45,257,360		45,257,360			177,782,000
Convertible Debt [Abstract]
Principal	$ 153,500,000		$ 153,500,000
PIK interest	19,371,000		19,371,000
Total principal	172,871,000		172,871,000
Less debt discount and issuance costs/plus debt premium	4,864,000		4,864,000
Total debt	177,735,000		177,735,000				$ 122,692,000
Fair value of debt	$ 313,400,000		$ 313,400,000
Convertible debt | Convertible Notes Facility | Forecast
Debt Instrument [Line Items]
Covenant, required minimum liquidity					$ 75,000,000
Covenant, required minimum liquidity, multiple factor of cash burn					4
Convertible debt | Conversion scenario one | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 4		$ 4
Percentage of principal amount to convert	33.33%		33.33%
Convertible debt | Conversion scenario two | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 5		$ 5
Percentage of principal amount to convert	33.33%		33.33%
Convertible debt | Conversion scenario three | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 6		$ 6
Convertible debt | Conversion scenario four | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 4		$ 4
Percentage of principal amount to convert	33.33%		33.33%
Convertible debt | Conversion scenario five | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 5		$ 5
Percentage of principal amount to convert	33.33%		33.33%
Convertible debt | Conversion scenario six | Convertible Notes Facility
Debt Instrument [Line Items]
Convertible Notes, conversion price (in usd per share) | $ / shares	$ 6		$ 6
Convertible debt | Volume weighted average price, period one | Convertible Notes Facility
Debt Instrument [Line Items]
Conversion provision, volume weighted average price (in usd per share) | $ / shares	15		15
Convertible debt | Volume weighted average price, period two | Convertible Notes Facility
Debt Instrument [Line Items]
Conversion provision, volume weighted average price (in usd per share) | $ / shares	$ 12		$ 12
Convertible debt | Additional Paid-in Capital | Convertible Notes
Debt Instrument [Line Items]
Principal and interest reclassified to additional paid-in capital		$ 48,800,000

Debt - Future Principal Repayme

Debt - Future Principal Repayments (Details) $ in Thousands	Mar. 31, 2023 USD ($)
Debt Disclosure [Abstract]
2023	$ 0
2024	0
2025	3,941
2028	168,930
Total debt	$ 172,871

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Leases [Abstract]
Operating lease, expense	$ 2.1	$ 1.5
Operating lease, weighted average remaining lease term	6 years 4 months 24 days		6 years 4 months 24 days
Operating lease, weighted average discount rate, percent	6.10%		6.20%

Leases - Net Investment In Leas

Leases - Net Investment In Lease (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Net investment in leases, current	$ 872	$ 985
Net investment in leases, non-current	9,173	9,304
Total net investment in leases	$ 10,045	$ 10,289

Leases - Lessor Future Minimum

Leases - Lessor Future Minimum Payments Receivable (Details) $ in Thousands	Mar. 31, 2023 USD ($)
Operating leases
Remainder of 2023	$ 279
2024	0
2025	0
2026	0
2027	0
Thereafter	0
Total minimum lease payments	279
Sales-type leases
Remainder of 2023	580
2024	1,010
2025	1,528
2026	1,528
2027	1,528
Thereafter	4,013
Total minimum lease payments	$ 10,187

Leases - Maturities Of Operatin

Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Remainder of 2023	$ 6,122
2024	4,224
2025	3,487
2026	2,615
2027	2,238
Thereafter	9,858
Total undiscounted lease payment	28,544
Less: imputed interest	(5,305)
Total operating lease liabilities	$ 23,239	$ 24,974

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ (2,082)	$ (1,377)
Lease liabilities arising from obtaining right-of-use assets:
Operating lease	0	25
Finance lease	$ 699	$ 0

Leases - Operating Lease Right-

Leases - Operating Lease Right-of-use Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Operating leases
Operating lease right-of-use assets	$ 18,661	$ 20,274	[1]
Operating lease liabilities, current	5,998	6,876	[1]
Operating lease liabilities, non-current	17,241	18,098	[1]
Total operating lease liabilities	$ 23,239	$ 24,974
[1]Derived from audited Consolidated Financial Statements.

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	[1]
Commitments and Contingencies Disclosure [Abstract]
Purchase commitment, outstanding inventory and other	$ 2,100,000
Long-term inventory prepayment	10,000	$ 10,000
Senior Credit Facility | Line of credit
Other Commitments [Line Items]
Letters of credit outstanding, amount	$ 20,200
[1]Derived from audited Consolidated Financial Statements.

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details)	3 Months Ended
	Mar. 31, 2023 vote shares	Dec. 31, 2022 shares	Jun. 14, 2021 $ / shares shares
Equity [Abstract]
Capital stock, shares authorized (in shares)			510,000,000
Capital stock, par value (in dollars per share) | $ / shares			$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	500,000,000	500,000,000
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000	10,000,000
Common stock, shares issued (in shares)	226,852,590	226,265,000
Common stock, shares outstanding (in shares)	226,852,590	226,265,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, number of votes per share | vote	1

Stockholders' Equity - Reserved

Stockholders' Equity - Reserved Shares (Details) shares in Thousands	Mar. 31, 2023 shares
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	114,312
2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	5,463
Warrants
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	1
Earnout Stock
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	18,009
Convertible notes
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	45,257
2010 Equity Incentive Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	16,331
2021 Equity Incentive Plan
Class of Stock [Line Items]
Common stock reserved for issuance (in shares)	29,251

Equity Plans and Stock-based _3

Equity Plans and Stock-based Compensation - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended
	Jun. 14, 2021	Jun. 11, 2021	Jun. 30, 2021	Mar. 31, 2020	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Number of options (in shares)					12,216,812
Stock-based compensation expense					$ 4,314,000	$ 4,642,000
Awards granted (in shares)					2,075,398
Awards outstanding (in shares)					15,912,092		14,256,697
Total intrinsic value of stock options exercised					$ 100,000
Total estimated grant date fair value of stock options vested					2,400,000
Unrecognized stock-based compensation expense, stock options					$ 11,700,000
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)					9,050,606	8,878,388
Percent of fair market value for greater than ten percent shareholders					110%
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)					2,262,651	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					$ 300,000	$ 300,000
2010 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable, Number of options (in shares)					16,331,367
2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares that may be issued (in shares)					30,000,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period					10 years
Award vesting period					4 years
Unrecognized stock-based compensation expense, period for recognition					2 years 7 months 6 days
Stock options | Greater Than Ten Percent Stockholder
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period					5 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					$ 34,200,000
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		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		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	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2023	Dec. 31, 2022
Number of Stock Options Outstanding
Balance at beginning of period (in shares)		14,256,697
Granted (in shares)		2,075,398
Exercised (in shares)		(57,036)
Cancelled/forfeited/expired (in shares)		(362,967)
Balance at end of period (in shares)		15,912,092	14,256,697
Options exercisable, Number of options (in shares)		12,216,812
Weighted- Average Exercise Price
Balance at beginning of period (in dollars per share)		$ 4.32
Granted (in dollars per share)		1.50
Exercised (in dollars per share)		1.98
Cancelled/forfeited/expired (in dollars per share)		6.67
Balance at end of period (in dollars per share)		3.91	$ 4.32
Options exercisable, Weighted average exercise price per share (in dollars per share)		$ 3.96
Stock Options, Additional Disclosures
Options outstanding, Weighted average remaining contractual term		5 years 7 months 6 days	5 years 6 months
Options exercisable, Weighted average remaining contractual term		4 years 6 months
Options outstanding, Aggregate intrinsic value		$ 372	$ 9,469
Options exercisable, Aggregate intrinsic value		$ 331
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	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	669,375
Equity Awards
Number of Stock Options Outstanding
Balance at end of period (in shares)		2,008,124
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	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 3 months 18 days	6 years 1 month 6 days
Risk-free interest rate	3.60%	1.90%
Expected volatility	55.10%	55%
Expected dividend rate	0%	0%

Equity Plans and Stock-based _6

Equity Plans and Stock-based Compensation - RSU Activity (Details) - Restricted stock units (RSUs)	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Number of RSUs
Balance at beginning of period (in shares) | shares	5,733,227
Granted (in shares) | shares	3,825,133
Released (in shares) | shares	(530,393)
Forfeited (in shares) | shares	(521,679)
Balance at end of period (in shares) | shares	8,506,288
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 7.07
Granted (in dollars per share) | $ / shares	1.75
Released (in dollars per share) | $ / shares	7.17
Forfeited (in dollars per share) | $ / shares	7.72
Balance at end of period (in dollars per share) | $ / shares	$ 4.63

Equity Plans and Stock-based _7

Equity Plans and Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 4,314	$ 4,642
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	305	516
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	1,192	993
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 2,817	$ 3,133

Net Loss Per Share - Calculatio

Net Loss Per Share - Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net loss	$ (243,977)	$ (50,078)
Effect of dilutive securities:
Interest expense to be recognized upon conversion of Convertible Notes	0	(55,185)
Numerator for diluted EPS - Net loss after the effect of dilutive securities	$ (243,977)	$ (105,263)
Denominator:
Weighted-average shares used in computing net loss per share of common stock, basic (in shares)	226,410	222,276
Convertible Notes (in shares)	0	24,855
Diluted weighted average shares (in shares)	226,410	247,131
Net loss per share of common stock:
Basic (in dollars per share)	$ (1.08)	$ (0.23)
Diluted (in dollars per share)	$ (1.08)	$ (0.43)
Convertible debt
Debt Instrument [Line Items]
Write off of unamortized debt issuance cost		$ 62,300
Interest expense		$ 7,100

Net Loss Per Share - Potentiall

Net Loss Per Share - Potentially Dilutive Securities (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2023 shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	63,301
Stock options and RSUs to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	27,765
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	1
Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	35,535

401(k) Plan (Details)

401(k) Plan (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Retirement Benefits [Abstract]
Employer matching contribution, percent of match	4%
Employer matching contribution, cost	$ 1.1	$ 0.7