Revenue

6 Months Ended

Jun. 30, 2022

Revenue

Revenue

13. Revenue

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,
	2022		2021		2022		2021
Sales of fuel cell systems	$	33,411	$	55,482	$	70,940	$	81,161
Sales of hydrogen infrastructure		32,414		40,109		59,502		60,462
Sales of electolyzers		3,675		3,687		7,734		4,427
Sales of engineered equipment		28,556		—		50,524		—
Services performed on fuel cell systems and related infrastructure		8,822		5,675		17,062		11,720
Power Purchase Agreements		11,169		8,361		21,206		16,187
Fuel delivered to customers and related equipment		14,472		11,121		27,900		22,248
Sales of cryogenic equipment		18,177		—		36,380		—
Other		571		122		822		310
Net revenue	$	151,267	$	124,557	$	292,070	$	196,515

Contract balances

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

	June 30,		December 31,
	2022		2021
Accounts receivable	$	61,502	$	92,675
Contract assets		39,143		38,757
Contract liabilities		127,705		183,090

Contract assets relate to contracts for which revenue is recognized on a straight-line basis; however, billings escalate over the life of a contract. Contract assets also include amounts recognized as revenue in advance of billings to customers, which are dependent upon the satisfaction of another performance obligation. These amounts are included in contract assets on the accompanying unaudited interim condensed consolidated balance sheets.

The contract liabilities relate to the advance consideration received from customers for services that will be recognized over time (primarily fuel cell and related infrastructure services) and advance consideration received from customers prior to delivery of products. These amounts are included within deferred revenue and other contract liabilities on the unaudited interim condensed consolidated balance sheets.

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, 2022		December 31, 2021
Transferred to receivables from contract assets recognized at the beginning of the period	$	(12,096)	$	(14,638)
Contract assets assumed as part of acquisition		—		9,960
Revenue recognized and not billed as of the end of the period		12,482		25,246
Net change in contract assets	$	386	$	20,568

Contract liabilities	Six months ended
	June 30, 2022		December 31, 2021
Increases due to cash received, net of amounts recognized as revenue during the period	$	41,170	$	182,052
Contract liabilities assumed as part of acquisitions		3,818		35,727
Revenue recognized that was included in the contract liability balance as of the beginning of the period		(100,373)		(110,974)
Net change in contract liabilities	$	(55,385)	$	106,805

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 Power Purchase Agreements (“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, net of the provision for common stock warrants (in thousands):

	June 30,
	2022
Sales of fuel cell systems	$	14,758
Sales of hydrogen installations and other infrastructure		17,781
Sales of electrolyzers		77,061
Sales of engineered equipment		48,607
Services performed on fuel cell systems and related infrastructure		93,371
Power Purchase Agreements		252,003
Fuel delivered to customers and related equipment		81,785
Sales of cryogenic equipment		59,599
Total estimated future revenue	$	644,965

Contract costs

Contract costs consist of capitalized commission fees and other expenses related to obtaining or fulfilling a contract. Capitalized contract costs at June 30, 2022 and December 31, 2021 were $0.6 million and $0.4 million, respectively.