| Cover Page Document | Feb. 24, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Feb. 24, 2020 |
| Entity Registrant Name | Sunnova Energy International Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38995 |
| Entity Tax Identification Number | 30-1192746 |
| Entity Address, Address Line One | 20 East Greenway Plaza, Suite 475 |
| 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 | 985-9904 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | NOVA |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001772695 |
| Amendment Flag | false |
