Revenue (Tables)

12 Months Ended

Dec. 31, 2019

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		2017
Sales of fuel cell systems	$	130,721	$	75,146	$	49,206
Sale of hydrogen installations and other infrastructure		19,163		32,146		13,425
Services performed on fuel cell systems and related infrastructure		25,217		22,002		16,202
Power Purchase Agreements		25,853		22,869		12,869
Fuel delivered to customers		29,099		22,469		8,167
Other		186		—		284
Net revenue	$	230,239	$	174,632	$	100,153

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):

	2019		2018
Accounts receivable	$	25,448	$	37,347
Contract assets		13,251		3,328
Contract liabilities		43,480		40,476

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, 2019
Transferred to receivables from contract assets recognized at the beginning of the period	$	(1,252)
Revenue recognized and not billed as of the end of the period		11,175
Net change in contract assets	$	9,923

Contract liabilities	Year ended
	December 31, 2019
Revenue recognized that was included in the contract liability balance as of the beginning of the period	$	(10,172)
Increases due to cash received, net of amounts recognized as revenue during the period		13,175
Net change in contract liabilities	$	3,003

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):

	Year ended December 31,
	2019		2018
Sales of fuel cell systems	$	73,491	$	17,318
Sale of hydrogen installations and other infrastructure		72,862		9,141
Services performed on fuel cell systems and related infrastructure		87,020		73,381
Power Purchase Agreements		133,475		111,533
Other rental income		4,993		6,633
Total estimated future revenue	$	371,841	$	218,006