Registry, engineering, and operating metrics shown on a consistent EIA basis.
| Metric | Helms Pumped Storage | Mammoth Pool |
|---|---|---|
| 1,053 MW | 190 MW | |
| Hydroelectric Pumped Storage | Conventional Hydroelectric | |
| Pacific Gas & Electric Co. | Southern California Edison Co | |
| 3 | 2 | |
| 1.11 TWh | 571.5 GWh | |
| — | 28.0% (2025) | |
| #8 of 39 | #73 of 1,349 | |
| 2026-06 | 2026-06 |