Diablo
Whatcom County, Washington · EIA plant ID 6432 · Operator: City of Seattle - (WA)
Nameplate182MWSummer 182 MW
Generators4in service
Net generation518GWh12 mo to Dec 2025
Capacity factor32%hydro units, summer MW
Heat rate—thermal plants only
First online1936
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 | 476.5 | 34.3% | — |
| 2002 | 898.9 | 64.6% | — |
| 2003 | 742.9 | 53.4% | — |
| 2004 | 776.4 | 55.7% | — |
| 2005 | 653.6 | 44.1% | — |
| 2006 | 744.2 | 50.2% | — |
| 2007 | 833.7 | 56.2% | — |
| 2008 | 754.7 | 55.9% | — |
| 2009 | 689.4 | 51.5% | — |
| 2010 | 718.6 | 48.7% | — |
| 2011 | 918.9 | 62.3% | — |
| 2012 | 935.6 | 63.2% | — |
| 2013 | 826.3 | 56.0% | — |
| 2014 | 856.1 | 58.0% | — |
| 2015 | 773.7 | 52.4% | — |
| 2016 | 869.1 | 58.8% | — |
| 2017 | 691.6 | 46.9% | — |
| 2018 | 624.8 | 39.1% | — |
| 2019 | 609.8 | 38.2% | — |
| 2020 | 702.5 | 43.9% | — |
| 2021 | 845.6 | 52.9% | — |
| 2022 | 588.9 | 36.9% | — |
| 2023 | 548.9 | 34.4% | — |
| 2024 | 361.4 | 22.6% | — |
| 2025 | 518.2 | 32.4% | — |
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 |
|---|---|---|---|---|---|---|---|---|
| 31 | Conventional Hydroelectric | HY | 90 | 90 | Apr 1937 | Operating | — | coming soon |
| 32 | Conventional Hydroelectric | HY | 90 | 90 | Oct 1936 | Operating | — | coming soon |
| 35 | Conventional Hydroelectric | HY | 1.2 | 1.2 | Oct 1936 | Operating | — | coming soon |
| 36 | Conventional Hydroelectric | HY | 1.2 | 1.2 | Oct 1936 | Operating | — | coming soon |
Owner / operator
Operator: City of Seattle - (WA). Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| City of Seattle - (WA) | 100.0% | 182 MW |
Nearby plants
Within 80 km.
| Ross | 450 MW | 5.1 km |
| Gorge | 207 MW | 5.9 km |
| Newhalem | 2 MW | 9 km |
| Upper Baker | 105 MW | 41.7 km |
| Koma Kulshan Associates | 12 MW | 43.6 km |
| Lower Baker | 104 MW | 48.4 km |