Revenue Recognition

Deferred Revenue and Customer Deposits

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



	March 31, 2020		December 31, 2019

Deferred revenue	$	170,034	$	168,223
Deferred incentive revenue	7,232		7,397
Customer deposits	42,707		39,101
Deferred revenue and customer deposits	$	219,973	$	214,721

Deferred revenue activity during the quarters ended March 31, 2020 and 2019 consisted of the following (in thousands):



	March 31, 2020			March 31, 2019
				As Restated
Beginning balance	$	168,223		$	140,130
Additions	138,113			118,359
Revenue recognized	(136,302		)	(117,755		)
Ending balance	$	170,034		$	140,734

Deferred revenue is equivalent to the total transaction price allocated to the performance obligations that are unsatisfied, or partially unsatisfied, as of March 31, 2020. The most 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 which 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.

Revenue by source

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



	Three Months Ended March 31,
	2020		2019
			As Restated
Revenue from contracts with customers:
Product revenue	$	99,559	$	90,926
Installation revenue	16,618		12,219
Services revenue	25,147		23,467
Electricity revenue	—		3,418
Total revenue from contract with customers	141,324		130,030
Revenue from contracts accounted for as leases:
Electricity revenue	15,375		16,971
Total revenue	$	156,699	$	147,001