Revenue Recognition

12 Months Ended

Dec. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue Recognition

Revenue Recognition

Deferred Revenue and Customer Deposits

Deferred revenue and customer deposits as of December 31, 2020 and 2019 consists of the following (in thousands):

	December 31,
	2020		2019
Deferred revenue	$	135,578	$	175,619
Customer deposits	66,171		39,101
Deferred revenue and customer deposits	$	201,749	$	214,720

Deferred revenue activity during the years ended December 31, 2020 and 2019 consists of the following (in thousands):

	Years Ended December 31,
	2020		2019
Beginning balance	$	175,619	$	149,612
Additions	652,960		709,843
Revenue recognized	(693,001)		(683,836)
Ending balance	$	135,578	$	175,619

Deferred revenue is equivalent to the total transaction price allocated to the performance obligations that are unsatisfied, or partially unsatisfied, as of the end of the period. The significant component of deferred revenue at the end of the period consists of performance obligations relating to the provision of maintenance services under current contracts and future renewal periods. These obligations provide customers with material rights over a period that we estimate will be largely commensurate with the period of their expected use of the associated Energy Server. As a result, we expect to recognize these amounts as revenue over a period of up to 21 years, predominantly on a cost-to-cost basis that reflects the cost of providing these services. Deferred revenue also includes performance obligations relating to product acceptance and installation. A significant amount of this deferred revenue is reflected as additions and revenue recognized in the same period and we expect to recognize all amounts within a year. During the year ended December 31, 2020, we recognized $14.2 million of previously deferred revenue that was not associated with acceptances or service in the year as a result of a modification of a contract with a customer.

We do not disclose the value of the unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed.

We disaggregate revenue from contracts with customers into four revenue categories: (i) product, (ii) installation, (iii) services, and (iv) electricity (in thousands):

	Years Ended December 31,
	2020		2019		2018
	Under ASC 606		With Adoption of ASC 606		Under ASC 605
Revenue from contracts with customers:
Product revenue	$	518,633	$	557,336	$	400,638
Installation revenue	101,887		60,826		68,195
Services revenue	109,633		95,786		83,267
Electricity revenue	—		10,840		23,023
Total revenue from contract with customers	730,153		724,788		575,123
Revenue from contracts accounted for as leases:
Electricity revenue	64,094		60,389		57,525
Total revenue	$	794,247	$	785,177	$	632,648