| Cover | Aug. 25, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 25, 2023 |
| Entity Registrant Name | Heliogen, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-40209 |
| Entity Tax Identification Number | 85-4204953 |
| Entity Address, Address Line One | 130 West Union Street |
| Entity Address, City or Town | Pasadena |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 91103 |
| City Area Code | 626 |
| Local Phone Number | 720-4530 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Entity Central Index Key | 0001840292 |
| Amendment Flag | false |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.0001 par value per share |
| Trading Symbol | HLGN |
| Security Exchange Name | NYSE |
| Warrant | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each whole warrant exercisable for shares of Common stock at an exercise price of $11.50 per share |
| Trading Symbol | HLGN.W |
| Security Exchange Name | NYSE |
| Preferred Share Purchase Right | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Preferred Share Purchase Rights |
| No Trading Symbol Flag | true |
| Security Exchange Name | NYSE |
