Markham
Mayes County, Oklahoma · EIA plant ID 2980 · Operator: Grand River Dam Authority
Nameplate128MWSummer 127 MW
Generators4in service
Net generation288GWh12 mo to Dec 2025
Capacity factor26%hydro units, summer MW
Heat rate—thermal plants only
First online1964
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 | 176.1 | 17.6% | — |
| 2002 | 150.9 | 15.1% | — |
| 2003 | 112.3 | 11.2% | — |
| 2004 | 288 | 28.8% | — |
| 2005 | 272.7 | 27.3% | — |
| 2006 | 39.6 | 4.0% | — |
| 2007 | 272.7 | 27.3% | — |
| 2008 | 403.1 | 40.3% | — |
| 2009 | 378.2 | 36.9% | — |
| 2010 | 277.8 | 26.2% | — |
| 2011 | 170.8 | 16.1% | — |
| 2012 | 95.6 | 9.0% | — |
| 2013 | 253.7 | 23.4% | — |
| 2014 | 111.3 | 9.9% | — |
| 2015 | 347.7 | 31.0% | — |
| 2016 | 251.7 | 22.4% | — |
| 2017 | 248.6 | 22.2% | — |
| 2018 | 176.3 | 15.7% | — |
| 2019 | 549.2 | 49.0% | — |
| 2020 | 337.9 | 30.0% | — |
| 2021 | 287.7 | 25.7% | — |
| 2022 | 210.8 | 18.8% | — |
| 2023 | 123.5 | 11.3% | — |
| 2024 | 188.2 | 17.0% | — |
| 2025 | 288.1 | 25.8% | — |
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 | 32.1 | 31.7 | May 1964 | Operating | — | coming soon |
| 2 | Conventional Hydroelectric | HY | 32.1 | 31.9 | May 1964 | Operating | — | coming soon |
| 3 | Conventional Hydroelectric | HY | 32.1 | 32 | May 1964 | Operating | — | coming soon |
| 4 | Conventional Hydroelectric | HY | 32.1 | 31.8 | May 1964 | Operating | — | coming soon |
Owner / operator
Operator: Grand River Dam Authority. Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| Grand River Dam Authority | 100.0% | 128 MW |
Nearby plants
Within 80 km.
| Salina | 259 MW | 7.9 km |
| Chouteau | 1,070 MW | 8.6 km |
| Grand River Energy Center Solar | — | 10.3 km |
| GREC | 1,788 MW | 10.7 km |
| Saltbranch Solar 1 | 73 MW | 11.9 km |
| Twelvemile Solar 2 | 52 MW | 11.9 km |