Mossyrock
Hydro power plant in Lewis County, Washington. 300 MW of nameplate capacity across 2 generators, operated by City of Tacoma - (WA).
Also known as EIA plant 3918
Analyst: free account, 1 question a day.
Key facts
- Capacity
- 300 MWNameplate
- Generators
- 2 operatingEIA-860M, August 2026
- Operating since
- October 1968First generator online
- Operator
- City of Tacoma - (WA)EIA operator ID 18429
- Grid
- TPWRBalancing authority TPWR
- Price nodes
- None linkedNo verified ISO node
- Location
- Lewis County, WA46.5347, −122.4247
- EIA plant ID
- 3918EIA plant page
Data as of EIA-860M August 2026 (published 2026-09-24). Capacity is nameplate, not live output.
How much power Mossyrock produces
Free · EIA-923Net generation, 2025
903 GWh
902,717 MWh, final
Capacity factor, 2025
34.3%
2024: 30.8%
January to July 2026
663 GWh
Provisional
Range, 2015 to 2025
0.6–1.3
TWh a year. Low 2019, high 2017
| Year | Net generation, MWh | Capacity factor | Months reported |
|---|---|---|---|
| 2000 | 963,370 | Not reported | 12 of 12 |
| 2001 | 485,753 | Not reported | 12 of 12 |
| 2002 | 1,059,808 | Not reported | 12 of 12 |
| 2003 | 965,731 | Not reported | 12 of 12 |
| 2004 | 749,599 | Not reported | 12 of 12 |
| 2005 | 538,106 | Not reported | 12 of 12 |
| 2006 | 1,161,783 | Not reported | 12 of 12 |
| 2007 | 940,545 | Not reported | 12 of 12 |
| 2008 | 1,003,098 | Not reported | 12 of 12 |
| 2009 | 995,862 | Not reported | 12 of 12 |
| 2010 | 1,026,686 | 39.1% | 12 of 12 |
| 2011 | 1,325,517 | 50.4% | 12 of 12 |
| 2012 | 1,416,781 | 53.8% | 12 of 12 |
| 2013 | 1,075,918 | 40.9% | 12 of 12 |
| 2014 | 1,286,970 | 49.0% | 12 of 12 |
| 2015 | 1,006,572 | 38.3% | 12 of 12 |
| 2016 | 1,202,136 | 45.6% | 12 of 12 |
| 2017 | 1,265,565 | 48.2% | 12 of 12 |
| 2018 | 907,773 | 34.5% | 12 of 12 |
| 2019 | 583,455 | 22.2% | 12 of 12 |
| 2020 | 1,110,279 | 42.1% | 12 of 12 |
| 2021 | 1,048,628 | 39.9% | 12 of 12 |
| 2022 | 1,125,647 | 42.8% | 12 of 12 |
| 2023 | 713,363 | 27.1% | 12 of 12 |
| 2024 | 811,561 | 30.8% | 12 of 12 |
| 2025 | 902,717 | 34.3% | 12 of 12 |
| 2026 (provisional, partial year) | 663,093 | 43.4% | 7 of 7 |
* 2026 covers January to July and is provisional. Capacity factor is net generation divided by nameplate capacity times the hours of each reported month.
Power prices and basis
Free accountNo verified ISO price node is linked to this plant, or its price history could not load.
Emissions
Free · EPA CAMPDNo EPA emissions units are linked to this plant.
Water use
Free · EIA-923 cooling, USGSNo EIA cooling-water record for this plant in 2024. Plants without steam cooling, such as wind, solar and batteries, do not report cooling water.
Generators
Free · EIA-860M| Generator | Technology | Nameplate MW | Online since |
|---|---|---|---|
| 51 | Conventional Hydroelectric | 150.0 | November 1968 |
| 52 | Conventional Hydroelectric | 150.0 | October 1968 |
Ownership and offtake
ProOwnership and offtake are part of Pro
Owners and their shares, parent companies, and power purchase agreements with their buyers. EIA-860M lists City of Tacoma - (WA) as the operator, which is not always the owner.
Modeled data
ProPro adds modeled values for this plant. Everything above stays free.
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Power plants near Mossyrock
More plants operated by City of Tacoma - (WA)
Questions about Mossyrock
How much power does Mossyrock produce?
Mossyrock reported 902,717 MWh (903 GWh) of net generation in 2025, a 34.3% capacity factor on 300 MW of nameplate capacity. From January to July 2026 it reported 663 GWh, which is provisional.
Where is Mossyrock?
Mossyrock is in Lewis County, Washington, at 46.5347, −122.4247. It is in the City of Tacoma, Department of Public Utilities, Light Division balancing area (TPWR).
Who operates Mossyrock?
EIA-860M for August 2026 lists City of Tacoma - (WA) as the operator (EIA operator ID 18429). The operator is not always the owner.
When did Mossyrock start operating?
Its first generator began operating in October 1968, according to EIA-860M.
Sources
- EIA-860 2025 (final) and EIA-860M August 2026: plant, generators, capacity, operator and location
- EIA-923 monthly net generation, 2000 to July 2026 (2026 provisional)
Page updated 2026-10-04 from the InfraMap data build. Methodology · Data sources · EIA plant page