Balance Sheet Components

Inventories

The components of inventory consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Raw materials	$	67,829	$	50,856
Work-in-progress	21,207		18,676
Finished goods	20,570		65,733
	$	109,606	$	135,265

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Government incentives receivable	$	893	$	1,001
Prepaid HW & SW maintenance	3,763		1,464
Receivables from employees	6,130		5,922
Other prepaid expense and other current assets	17,282		28,360
	$	28,068	$	36,747

Property, Plant and Equipment, Net

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2019			2018
				As Restated
Energy Servers	$	650,600		$	757,574
Computers, software and hardware	20,275			16,536
Machinery and equipment	101,650			99,209
Furniture and fixtures	8,339			4,337
Leasehold improvements	35,694			18,629
Building	40,512			40,512
Construction in progress	12,611			41,180
	869,681			977,977
Less: Accumulated depreciation	(262,622		)	(261,226		)
	$	607,059		$	716,751

Construction in progress decreased $28.6 million from 2018, primarily due to our move to our new corporate headquarters during the first quarter of 2019. After the move was completed, $17.6 million was reclassified to leasehold improvements within property, plant and equipment. In addition, the remaining decrease of $11.0 million was due to acceptances of Energy Servers under our Managed Services sale-leaseback program which are reclassified from construction in progress to Energy Servers within property, plant and equipment upon acceptance.

Depreciation expense related to property, plant and equipment was $78.6 million, $53.1 million and $54.4 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Property, plant and equipment under operating leases by the PPA Entities was $371.4 million and $397.5 million as of December 31, 2019 and 2018, respectively. The accumulated depreciation for these assets was $95.5 million and $77.4 million as of December 31, 2019 and 2018, respectively. Depreciation expense related to our property, plant and equipment under operating leases by the PPA Entities was $27.1 million, $25.5 million and $25.5 million for the years ended December 31, 2019, 2018 and 2017 respectively.

During the year ended December 31, 2019, there was a decommissioning in PPA II, including the replacement during 2019 of 30.0 megawatts of installed Energy Servers with 27.5 megawatts of new systems sold, resulting in product cost of goods sold due to $52.5 million for the write-off of Energy Servers and $78.4 million for the cost of new systems sold, and electricity cost of revenue of $22.6 million of accelerated depreciation charged.

During the year ended December 31, 2019, there was a decommissioning in PPA IIIb, including the replacement during 2019 of 5.0 megawatts of installed Energy Servers, resulting in product cost of goods sold of $18.0 million for the write-off of Energy Servers, and electricity cost of revenue of $1.7 million of accelerated depreciation charged in fourth quarter of 2019 related to the revised expected lives of installed systems, which we recognized in our consolidated statement of operations

See Note 13, Power Purchase Agreement Programs - PPA II Upgrade of Energy Servers and PPA IIIb Upgrade of Energy Servers for additional information.

Customer Financing Receivable

The components of investment in sales-type financing leases consisted of the following (in thousands):



	December 31,
	2019			2018
Total minimum lease payments to be received	$	76,886		$	100,816
Less: Amounts representing estimated executing costs	(19,931		)	(25,180		)
Net present value of minimum lease payments to be received	56,955			75,636
Estimated residual value of leased assets	890			1,051
Less: Unearned income	(1,990		)	(4,011		)
Net investment in sales-type financing leases	55,855			72,676
Less: Current portion	(5,108		)	(5,594		)
Non-current portion of investment in sales-type financing leases	$	50,747		$	67,082

The future scheduled customer payments from sales-type financing leases were as follows as of December 31, 2019 (in thousands):



	2020		2021		2022		2023		2024		Thereafter

Future minimum lease payments, less interest	$	5,108	$	5,428	$	5,784	$	6,155	$	6,567	$	25,923

Other Long-Term Assets

Other long-term assets consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Prepaid and other long-term assets	$	29,153	$	34,093
Deferred commissions	5,007		1,083
Equity-method investments	5,733		6,046
Long-term deposits	1,759		1,660
	$	41,652	$	42,882

Accrued Warranty

Accrued warranty liabilities consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Product warranty	$	2,345	$	3,378
Product performance	7,536		6,290
Maintenance services contracts	453		8,300
	$	10,334	$	17,968

Changes in the product warranty and product performance liabilities were as follows (in thousands):



Balances at December 31, 2016 (As Revised)	$	8,082
Accrued warranty, net (As Revised)	5,979
Warranty expenditures during period (As Revised)	(6,740		)
Balances at December 31, 2017 (As Revised)	7,321
Accrued warranty, net (As Restated)	9,301
Warranty expenditures during period (As Restated)	(6,954		)
Balances at December 31, 2018 (As Restated)	9,668
Cumulative effect upon adoption of ASC 606	1,032
Accrued warranty, net	1,849
Warranty expenditures during period	(2,668		)
Balances at December 31, 2019	$	9,881

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Compensation and benefits	$	17,173	$	16,742
Current portion of derivative liabilities	4,834		3,232
Sales related liabilities	416		1,421
Accrued installation	10,348		6,859
Sales tax liabilities	3,849		1,798
Interest payable	3,875		4,675
Other	29,789		32,111
	$	70,284	$	66,838

Other Long-Term Liabilities

Other long-term liabilities consisted of the following (in thousands):



	December 31,
	2019		2018
			As Restated
Delaware grant	$	10,469	$	10,469
Other	17,544		15,727
	$	28,013	$	26,196

In March 2012, we entered into an agreement with the Delaware Economic Development Authority to provide a grant of $16.5 million to us as an incentive to establish a new manufacturing facility in Delaware and to provide employment for full time workers at the facility over a certain period of time. We have received $12.0 million of the grant which is contingent upon us meeting certain milestones related to the construction of the manufacturing facility and the employment of full-time workers at the facility through September 30, 2023. As of December 31, 2019, we have paid $1.5 million in October 2017 for recapture provisions and have recorded $10.5 million in other long-term liabilities for potential repayments. See Note 14, Commitments and Contingencies for a full description of the grant.