| Cover | Dec. 30, 2021 |
| Entity Addresses [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 30, 2021 |
| Entity File Number | 001-40209 |
| Entity Registrant Name | Heliogen, Inc. |
| Entity Central Index Key | 0001840292 |
| Entity Tax Identification Number | 85-4204953 |
| Entity Incorporation, State or Country Code | DE |
| 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 | (970) |
| Local Phone Number | 924-0046 |
| Written Communications | true |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Common Stock, par value $0.0001 per share | |
| Entity Addresses [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | HLGN |
| Security Exchange Name | NYSE |
| Redeemable Warrants, exercisable for one share of Common Stock at an exercise price of $11.50 | |
| Entity Addresses [Line Items] | |
| Title of 12(b) Security | Redeemable Warrants, exercisable for one share of Common Stock at an exercise price of $11.50 |
| Trading Symbol | HLGN.W |
| Security Exchange Name | NYSE |
| Former Address [Member] | |
| Entity Addresses [Line Items] | |
| Entity Address, Address Line One | 125 Townpark Drive |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Kennesaw |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30144 |
