Lower Monumental
Walla Walla County, Washington · EIA plant ID 3927 · Operator: USACE Northwestern Division
Nameplate810MWSummer 810 MW
Generators6in service
Net generation1,504GWh12 mo to Aug 2026
Capacity factor21%hydro units, summer MW
Heat rate—thermal plants only
First online1969
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 | 1,922.7 | 23.5% | — |
| 2002 | 2,509.5 | 30.7% | — |
| 2003 | 2,104.3 | 25.8% | — |
| 2004 | 2,267.6 | 31.9% | — |
| 2005 | 1,850.1 | 26.1% | — |
| 2006 | 2,755.8 | 38.8% | — |
| 2007 | 1,682.6 | 23.7% | — |
| 2008 | 2,200.5 | 30.9% | — |
| 2009 | 2,416.9 | 34.1% | — |
| 2010 | 1,858.9 | 26.2% | — |
| 2011 | 3,295.3 | 46.4% | — |
| 2012 | 2,520.1 | 35.4% | — |
| 2013 | 1,697 | 23.9% | — |
| 2014 | 2,290.2 | 32.9% | — |
| 2015 | 1,640.1 | 23.6% | — |
| 2016 | 1,987.1 | 28.5% | — |
| 2017 | 2,767.6 | 42.9% | — |
| 2018 | 2,383.4 | 37.0% | — |
| 2019 | 2,240.9 | 34.0% | — |
| 2020 | 1,637.3 | 24.8% | — |
| 2021 | 1,338.5 | 19.3% | — |
| 2022 | 1,682.6 | 24.3% | — |
| 2023 | 1,553 | 21.9% | — |
| 2024 | 1,281 | 18.0% | — |
| 2025 | 1,477 | 20.8% | — |
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 | 135 | 135 | Jun 1969 | Operating | — | coming soon |
| 2 | Conventional Hydroelectric | HY | 135 | 135 | Oct 1969 | Operating (Out of service, expected back within the year) | — | coming soon |
| 3 | Conventional Hydroelectric | HY | 135 | 135 | Feb 1970 | Operating | — | coming soon |
| 4 | Conventional Hydroelectric | HY | 135 | 135 | Mar 1979 | Operating | — | coming soon |
| 5 | Conventional Hydroelectric | HY | 135 | 135 | Apr 1979 | Operating | — | coming soon |
| 6 | Conventional Hydroelectric | HY | 135 | 135 | Jul 1979 | Operating | — | coming soon |
Owner / operator
Operator: USACE Northwestern Division. Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| USACE Northwestern Division | 100.0% | 810 MW |
Nearby plants
Within 80 km.
| Little Goose | 810 MW | 39.2 km |
| Rattlesnake Flat | 144 MW | 42 km |
| Tucannon River Wind Farm | 267 MW | 42.3 km |
| Ice Harbor | 603 MW | 43.6 km |
| Adams Nielson Solar | 19 MW | 44 km |
| Russell D Smith | 6 MW | 47.9 km |