Revenue (Tables)

6 Months Ended

Jun. 30, 2021

Revenue

Schedule of disaggregation of revenue

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

Major products/services lines
	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Sales of fuel cell systems	$	59,169	$	40,785	$	85,588	$	55,425

Sale of hydrogen installations and other infrastructure		40,109		6,961		60,462		12,789
Services performed on fuel cell systems and related infrastructure		5,675		6,236		11,720		12,757
Power Purchase Agreements		8,361		6,579		16,187		13,000
Fuel delivered to customers		11,121		7,372		22,248		14,705
Other		122		62		310		138
Net revenue	$	124,557	$	67,995	$	196,515	$	108,814

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):

	June 30,		December 31,
	2021		2020
Accounts receivable	$	91,359	$	43,041
Contract assets		11,549		18,189
Contract liabilities		93,665		76,285

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	Six months ended
	June 30, 2021
Transferred to receivables from contract assets recognized at the beginning of the period	$	(7,106)
Revenue recognized and not billed as of the end of the period		466
Net change in contract assets		(6,640)

Contract liabilities	Six months ended
	June 30, 2021
Increases due to cash received, net of amounts recognized as revenue during the period	$	49,628
Revenue recognized that was included in the contract liability balance as of the beginning of the period		(32,248)
Net change in contract liabilities	$	17,380

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):

	June 30,
	2021
Sales of fuel cell systems	$	55,348
Sale of hydrogen installations and other infrastructure		52,193
Services performed on fuel cell systems and related infrastructure		103,505
Power Purchase Agreements		196,903
Fuel delivered to customers		63,632
Other rental income		2,504
Total estimated future revenue	$	474,085