| Document and Entity Information | Nov. 10, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 10, 2021 |
| Entity Registrant Name | CAPSTONE GREEN ENERGY CORPORATION |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-15957 |
| Entity Tax Identification Number | 95-4180883 |
| Entity Address, Address Line One | 16640 Stagg Street, |
| Entity Address, City or Town | Van Nuys |
| Entity Address State Or Province | CA |
| Entity Address, Postal Zip Code | 91406 |
| City Area Code | 818 |
| Local Phone Number | 734-5300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001009759 |
| Amendment Flag | false |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $.001 per share |
| Trading Symbol | CGRN |
| Security Exchange Name | NASDAQ |
| Series B Junior Participating Preferred Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series B Junior Participating Preferred Stock Purchase Rights |
| No Trading Symbol Flag | true |
