Mayfield
Lewis County, Washington · EIA plant ID 3917 · Operator: City of Tacoma - (WA)
Nameplate162MWSummer 164 MW
Generators4in service
Net generation603GWh12 mo to Dec 2025
Capacity factor42%hydro units, summer MW
Heat rate—thermal plants only
First online1963
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 | 430.1 | 28.5% | — |
| 2002 | 688.4 | 47.9% | — |
| 2003 | 646.3 | 45.0% | — |
| 2004 | 809.5 | 56.2% | — |
| 2005 | 748.7 | 52.1% | — |
| 2006 | 749.2 | 52.1% | — |
| 2007 | 647.2 | 45.1% | — |
| 2008 | 729.6 | 50.6% | — |
| 2009 | 75.3 | 5.2% | — |
| 2010 | 695.3 | 48.4% | — |
| 2011 | 828.5 | 57.7% | — |
| 2012 | 903.5 | 62.7% | — |
| 2013 | 714.5 | 49.7% | — |
| 2014 | 821.8 | 57.2% | — |
| 2015 | 621.1 | 43.2% | — |
| 2016 | 784.8 | 54.5% | — |
| 2017 | 870.9 | 60.6% | — |
| 2018 | 646 | 45.0% | — |
| 2019 | 448.8 | 31.2% | — |
| 2020 | 725.6 | 50.4% | — |
| 2021 | 724.8 | 50.4% | — |
| 2022 | 769.3 | 53.5% | — |
| 2023 | 545 | 37.9% | — |
| 2024 | 576.4 | 40.0% | — |
| 2025 | 602.5 | 41.9% | — |
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 |
|---|---|---|---|---|---|---|---|---|
| 41 | Conventional Hydroelectric | HY | 40.5 | 41 | May 1983 | Operating | — | coming soon |
| 42 | Conventional Hydroelectric | HY | 40.5 | 41 | Mar 1963 | Operating | — | coming soon |
| 43 | Conventional Hydroelectric | HY | 40.5 | 41 | Apr 1963 | Operating | — | coming soon |
| 44 | Conventional Hydroelectric | HY | 40.5 | 41 | Jun 1963 | Operating | — | coming soon |
Owner / operator
Operator: City of Tacoma - (WA). Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| City of Tacoma - (WA) | 100.0% | 162 MW |
Nearby plants
Within 80 km.
| Mossyrock | 300 MW | 13 km |
| Chehalis Generating Facility | 593 MW | 28.1 km |
| Skookumchuck | 1 MW | 32.8 km |
| Transalta Centralia Generation | 730 MW | 34.9 km |
| Cowlitz Falls | 70 MW | 36.9 km |
| Centralia Battery Energy Storage System | — | 38.2 km |