Revenue (Tables)

6 Months Ended

Jun. 30, 2020

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,
	2020		2019		2020		2019
Sales of fuel cell systems	$	41,264	$	38,696	$	55,915	$	41,240
Sale of hydrogen installations and other infrastructure		6,482		—		12,218		—
Services performed on fuel cell systems and related infrastructure		6,236		5,341		12,757		11,684
Power Purchase Agreements		6,654		6,409		13,150		12,519
Fuel delivered to customers		7,372		7,089		14,705		13,671
Other		62		—		138		—
Net revenue	$	68,070	$	57,535	$	108,883	$	79,114

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,
	2020		2019
Accounts receivable	$	45,522	$	25,448
Contract assets		20,481		13,251
Contract liabilities		50,233		43,480

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, 2020
Transferred to receivables from contract assets recognized at the beginning of the period	$	(9,671)
Revenue recognized and not billed as of the end of the period		16,901
Net change in contract assets		7,230

Contract liabilities	Six months ended
	June 30, 2020
Increases due to cash received, net of amounts recognized as revenue during the period	$	24,835
Revenue recognized that was included in the contract liability balance as of the beginning of the period		(18,082)
Net change in contract liabilities	$	6,753

Schedule of Estimated future revenue

The following table includes estimated revenue 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, excluding provision for common stock warrants as it is not readily estimable as it depends on the valuation of the common stock warrants when revenue is recognized (in thousands):

	June 30,
	2020
Sales of fuel cell systems	$	71,402
Sale of hydrogen installations and other infrastructure		71,753
Services performed on fuel cell systems and related infrastructure		94,725
Power Purchase Agreements		151,793
Other rental income		4,117
Total estimated future revenue	$	393,790