| Document and Entity Information | May 17, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001772695 |
| Document Type | 8-K |
| Document Period End Date | May 17, 2021 |
| Entity Registrant Name | Sunnova Energy International Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38995 |
| Entity Tax Identification Number | 30-1192746 |
| Entity Address, Address Line One | 20 East Greenway Plaza |
| Entity Address, Address Line Two | Suite 540 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77046 |
| City Area Code | (281) |
| Local Phone Number | 892-1588 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.0001 par value per share |
| Trading Symbol | NOVA |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
