Mammoth Pool
Madera County, California · EIA plant ID 344 · Operator: Southern California Edison Co
Nameplate190MWSummer 190 MW
Generators2in service
Net generation584GWh12 mo to Aug 2026
Capacity factor35%hydro units, summer MW
Heat rate—thermal plants only
First online1960
The 12-month figures include preliminary EIA-923 months, which EIA revises. Final data runs through Dec 2025.
Monthly net generation
EIA-923, all units at the plant. Net of station use; storage can go negative.
FinalPreliminary
Capacity factor by year
Net MWh ÷ (summer MW × hours), hydro units. Each year uses that year's EIA-860 ratings; the hollow dot is the latest 12 months.
Heat rate by year
Electric fuel MMBtu × 1000 ÷ net MWh (Btu/kWh, HHV), fossil units only; CT + CA counted as one combined-cycle block.
Heat rate applies to fuel-burning (thermal) units only.
Annual data table
| Year | Net GWh | Capacity factor | Heat rate (Btu/kWh) |
|---|---|---|---|
| 2001 | 429 | 26.2% | — |
| 2002 | 487 | 29.7% | — |
| 2003 | 513 | 31.3% | — |
| 2004 | 500.3 | 30.5% | — |
| 2005 | 675.6 | 41.2% | — |
| 2006 | 760.5 | 46.4% | — |
| 2007 | 259.1 | 15.8% | — |
| 2008 | 296.3 | 18.0% | — |
| 2009 | 541.9 | 33.1% | — |
| 2010 | 708.6 | 43.3% | — |
| 2011 | 753.9 | 48.4% | — |
| 2012 | 291 | 20.7% | — |
| 2013 | 355.7 | 25.4% | — |
| 2014 | 217.3 | 15.5% | — |
| 2015 | 137.6 | 9.8% | — |
| 2016 | 632.6 | 45.0% | — |
| 2017 | 970.3 | 69.2% | — |
| 2018 | 443.4 | 31.6% | — |
| 2019 | 513.5 | 30.9% | — |
| 2020 | 320.6 | 19.2% | — |
| 2021 | 293.3 | 17.6% | — |
| 2022 | 507.6 | 30.5% | — |
| 2023 | 449 | 27.0% | — |
| 2024 | 413.6 | 24.8% | — |
| 2025 | 465.9 | 28.0% | — |
Generators
EIA-860 (annual) with EIA-860M updates through Sep 2026. EIA-923 reports generation by plant, prime mover and fuel, not by unit, so unit-level output isn't shown.
| Gen ID | Technology | Prime mover | Nameplate MW | Summer MW | Online | Status | Planned retirement | OEM / model |
|---|---|---|---|---|---|---|---|---|
| 1 | Conventional Hydroelectric | HY | 95 | 95 | Mar 1960 | Operating | — | coming soon |
| 2 | Conventional Hydroelectric | HY | 95 | 95 | Mar 1960 | Operating | — | coming soon |
Owner / operator
Operator: Southern California Edison Co. Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| Southern California Edison Co | 100.0% | 190 MW |
Nearby plants
Within 80 km.
| Big Creek 8 | 75 MW | 1.4 km |
| Big Creek 2 | 67 MW | 3.6 km |
| Big Creek 2A | 110 MW | 3.6 km |
| Big Creek 1 | 88 MW | 8.9 km |
| Big Creek 3 | 175 MW | 9.1 km |
| J S Eastwood | 200 MW | 10.8 km |