Revenue (Tables)

9 Months Ended

Sep. 30, 2018

In the following table, revenue is disaggregated by major product line and timing of revenue recognition (in thousands):


Major products/services lines	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
Sales of fuel cell systems	$	21,595	$	28,427	$	40,948	$	35,190
Sale of hydrogen installations and other infrastructure		15,073		9,633		25,153		12,717
Services performed on fuel cell systems and related infrastructure		5,156		2,217		16,330		10,496
Power Purchase Agreements		5,555		(1,663)		16,365		7,593
Fuel delivered to customers		5,786		(4,149)		16,016		2,782
Other		—		128		—		279
Net revenue	$	53,165	$	34,593	$	114,812	$	69,057

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):


	September 30, 2018		December 31, 2017
Accounts receivable	$	24,721	$	15,331
Contract assets		7,727		9,316
Contract liabilities		39,605		35,171

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	Nine months ended
	September 30, 2018
Transferred to receivables from contract assets recognized at the beginning of the period	$	(6,032)
Revenue recognized and not billed as of the end of the period		4,443
Net change in contract assets	$	(1,589)


Contract liabilities	Nine months ended
	September 30, 2018
Revenue recognized that was included in the contract liability balance as the beginning of the period	$	7,882
Increases due to cash received, net of amounts recognized as revenue during the period		(12,316)
Net change in contract liabilities	$	(4,434)

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):


	September 30, 2018		December 31, 2017
Sales of fuel cell systems	$	21,029	$	26,298
Sale of hydrogen installations and other infrastructure		6,705		15,512
Services performed on fuel cell systems and related infrastructure		75,416		77,453
Power Purchase Agreements		114,757		130,042
Total estimated future revenue	$	217,907	$	249,305