Revenue

3 Months Ended

Mar. 31, 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 March 31,
	2022		2021
Sales of fuel cell systems	$	37,528	$	26,419
Sales of hydrogen infrastructure		27,089		20,353
Sales of electolyzers		4,059		—
Sales of oil and gas equipment		21,968		—
Services performed on fuel cell systems and related infrastructure		8,240		6,045
Power Purchase Agreements		10,037		7,826
Fuel delivered to customers		13,429		11,127
Sales of cryogenic equipment		18,203		—
Other		251		188
Net revenue	$	140,804	$	71,958

Contract balances

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

	March 31,		December 31,
	2022		2021
Accounts receivable	$	57,322	$	92,675
Contract assets		38,713		38,757
Contract liabilities		155,185		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	Three months ended
	March 31, 2022		December 31, 2021
Transferred to receivables from contract assets recognized at the beginning of the period	$	(3,693)	$	(14,638)
Contract assets assumed as part of acquisition		—		9,960
Revenue recognized and not billed as of the end of the period		3,649		25,246
Net change in contract assets	$	(44)	$	20,568

Contract liabilities	Three months ended
	March 31, 2022		December 31, 2021
Increases due to cash received, net of amounts recognized as revenue during the period	$	13,327	$	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		(45,050)		(110,974)
Net change in contract liabilities	$	(27,905)	$	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):

	March 31,
	2022
Sales of fuel cell systems	$	16,466
Sale of hydrogen installations and other infrastructure		40,487
Sale of electrolyzers		51,267
Sales of oil and gas equipment		73,270
Services performed on fuel cell systems and related infrastructure		98,635
Power Purchase Agreements		255,929
Fuel delivered to customers and related equipment		83,796
Sale of cryogenic equipment		62,299
Total estimated future revenue	$	682,149

Contract costs

Contract costs consist of capitalized commission fees and other expenses related to obtaining or fulfilling a contract. Capitalized contract costs at March 31, 2022 and March 31, 2021 were $0.5 million and $1.7 million, respectively.