Mystic
Stillwater County, Montana · EIA plant ID 2192 · Operator: NorthWestern Energy
Nameplate12MWSummer 12 MW
Generators2in service
Net generation52GWh12 mo to Dec 2025
Capacity factor50%hydro units, summer MW
Heat rate—thermal plants only
First online1925
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 | 38.8 | 46.6% | — |
| 2002 | 40.7 | 38.7% | — |
| 2003 | 45.1 | 41.5% | — |
| 2004 | 43.3 | 39.8% | — |
| 2005 | 42.6 | 39.2% | — |
| 2006 | 43.3 | 39.8% | — |
| 2007 | 48.6 | 44.7% | — |
| 2008 | 53.5 | 50.7% | — |
| 2009 | 54.4 | 51.8% | — |
| 2010 | 46.1 | 43.9% | — |
| 2011 | 50.6 | 48.1% | — |
| 2012 | 49.1 | 46.6% | — |
| 2013 | 54.1 | 51.5% | — |
| 2014 | 57.1 | 54.3% | — |
| 2015 | 57.5 | 54.7% | — |
| 2016 | 51.4 | 48.8% | — |
| 2017 | 61.9 | 58.9% | — |
| 2018 | 61.3 | 58.3% | — |
| 2019 | 57.8 | 55.0% | — |
| 2020 | 56.4 | 53.5% | — |
| 2021 | 52.9 | 50.4% | — |
| 2022 | 38.2 | 36.4% | — |
| 2023 | 62.3 | 59.3% | — |
| 2024 | 53.7 | 51.0% | — |
| 2025 | 52.5 | 49.9% | — |
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 |
|---|---|---|---|---|---|---|---|---|
| MYS1 | Conventional Hydroelectric | HY | 6 | 6 | May 1925 | Operating | — | coming soon |
| MYS2 | Conventional Hydroelectric | HY | 6 | 6 | May 1925 | Operating | — | coming soon |
Owner / operator
Operator: NorthWestern Energy. Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| NorthWestern Energy | 100.0% | 12 MW |
Nearby plants
Within 80 km.
| South Dry Creek Hydro | 2 MW | 46.8 km |
| River Bend Solar, LLC | 2 MW | 55.3 km |
| Big Timber Wind Farm | 25 MW | 70.6 km |
| Stillwater Wind, LLC | 80 MW | 74.6 km |
| Elk Basin Gasoline Plant | 1 MW | 77.2 km |