| Cover | Aug. 15, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 15, 2022 |
| Entity Registrant Name | FLUENCE ENERGY, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-40978 |
| Entity Tax Identification Number | 87-1304612 |
| Entity Address, Address Line One | 4601 Fairfax Drive |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | Arlington, |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 22203 |
| City Area Code | (833) |
| Local Phone Number | 358-3623 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, $0.00001 par value per share |
| Trading Symbol | FLNC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001868941 |
| Amendment Flag | false |
