Schedule I Parent Company Financial Statements - Condensed Balance Sheets (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash		$ 243,101	$ 209,859	$ 83,485
Total current assets		615,742	456,655
Total assets	[1]	5,504,234	3,587,583
Current liabilities:
Accounts payable		55,033	39,908
Other current liabilities		44,350	26,014
Total current liabilities		310,897	210,854
Total liabilities	[1]	3,882,621	2,306,902
Stockholders' equity:
Common stock		11	10
Additional paid-in capital—common stock		1,649,199	1,482,716
Accumulated deficit		(459,715)	(530,995)
Total stockholders' equity		1,189,495	951,731
Total liabilities, redeemable noncontrolling interests and equity		5,504,234	3,587,583
Parent Company
Current assets:
Cash		518	4,917
Total current assets		518	4,917
Investments in subsidiaries		1,603,950	1,076,299
Total assets		1,604,468	1,081,216
Current liabilities:
Accounts payable		2	437
Other current liabilities		120	1,314
Total current liabilities		122	1,751
Long-term debt, net		561,643	58,015
Total liabilities		561,765	59,766
Stockholders' equity:
Common stock		11	10
Additional paid-in capital—common stock		1,629,208	1,462,690
Accumulated deficit		(586,516)	(441,250)
Total stockholders' equity		1,042,703	1,021,450
Total liabilities, redeemable noncontrolling interests and equity		$ 1,604,468	$ 1,081,216

[1] The consolidated assets as of December 31, 2021 and 2020 include $2,148,398 and $1,471,796, respectively, of assets of variable interest entities ("VIEs") that can only be used to settle obligations of the VIEs. These assets include cash of $23,538 and $13,407 as of December 31, 2021 and 2020, respectively; accounts receivable—trade, net of $6,167 and $2,953 as of December 31, 2021 and 2020, respectively; accounts receivable—other of $410 and $583 as of December 31, 2021 and 2020, respectively; other current assets of $272,421 and $182,646 as of December 31, 2021 and 2020, respectively; property and equipment, net of $1,817,471 and $1,257,953 as of December 31, 2021 and 2020, respectively; and other assets of $28,391 and $14,254 as of December 31, 2021 and 2020, respectively. The consolidated liabilities as of December 31, 2021 and 2020 include $47,225 and $32,345, respectively, of liabilities of VIEs whose creditors have no recourse to Sunnova Energy International Inc. These liabilities include accounts payable of $6,014 and $2,744 as of December 31, 2021 and 2020, respectively; accrued expenses of $88 and $827 as of December 31, 2021 and 2020, respectively; other current liabilities of $3,845 and $3,284 as of December 31, 2021 and 2020, respectively; and other long-term liabilities of $37,278 and $25,490 as of December 31, 2021 and 2020, respectively.