Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Revenue

Schedule of disaggregation of revenue

The following table provides information about disaggregation of revenue (in thousands):

Major products/services lines
	Year ended December 31,
			2019		2018
	2020		(as restated)		(as restated)
Sales of fuel cell systems	$	(55,091)	$	130,757	$	75,029
Sale of hydrogen infrastructure		(39,204)		19,163		32,146
Services performed on fuel cell systems and related infrastructure		(9,801)		25,217		22,002
Power Purchase Agreements		26,620		25,553		22,569
Fuel delivered to customers		(16,072)		29,099		22,469
Other		311		186		—
Net revenue	$	(93,237)	$	229,975	$	174,215

Schedule of receivables, contract assets and contract liabilities from contracts with customers

The following table provides information about receivables, contract assets and contract liabilities from contracts with customers (in thousands):

	2020		2019
Accounts receivable	$	43,041	$	25,768
Contract assets		18,189		13,251
Contract liabilities		76,285		40,743

Schedule of changes in contract assets and the contract liabilities

Significant changes in the contract assets and the contract liabilities balances during the period are as follows (in thousands):

Contract assets	Year ended
	December 31, 2020
Transferred to receivables from contract assets recognized at the beginning of the period	$	(5,483)
Revenue recognized and not billed as of the end of the period		10,421
Net change in contract assets	$	4,938

Contract liabilities	Year ended
	December 31, 2020
Increases due to cash received, net of amounts recognized as revenue during the period	$	100,492
Contract liabilities assumed as part of acquisitions		2,350
Revenue recognized that was included in the contract liability balance as of the beginning of the period		(67,300)
Net change in contract liabilities	$	35,542

Schedule of Estimated future revenue

The following table includes estimated revenue included in the backlog expected to be recognized in the future (sales of fuel cell systems and hydrogen installations are expected to be recognized as revenue within one year; sales of services and PPAs are expected to be recognized as revenue over five to seven years) related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period, including provision for common stock warrants (in thousands):

Estimated future revenue
	December 31,
	2020
Sales of fuel cell systems	$	16,209
Sale of hydrogen installations and other infrastructure		28,282
Services performed on fuel cell systems and related infrastructure		75,467
Power Purchase Agreements		178,450
Fuel delivered to customers		65,704
Other rental income		3,294
Total estimated future revenue	$	367,406