Big Stone
Big Stone is a coal plant in Grant County, South Dakota, operated by Otter Tail Power Co. It ranks third by nameplate capacity among South Dakota’s 54 power plants. Its biggest unit, rated at 450 MW, is the largest single generator in South Dakota. Ownership is shared by three organizations; the largest stake, 54%, is held by Otter Tail Power Co.
Nameplate capacity, 2025
451 MW
479 MW net summer capacity
2 operable units
- Coal steam450 MW100%
- Oil-fired1 MW0.2%
Unit by unit, 1975 to 2025
operating in 2025bar height follows unit size
Unit 1 Coal steam, 450 MW, 1975
Unit D1 Oil-fired, 1 MW, 1975
Among South Dakota’s plants
Largest plants in the state by nameplate capacity, with the plants ranked next to this one.
- 1Oahe786 MW
- 2Big Bend Dam538 MW
- 3Big Stonethis plant
- 4Angus Anson406 MW
- 5Astoria Station349 MW
Other rankings
- All US power plants
- 791st of 14,286
- US coal plants
- 124th of 195
- Plants in the MISO (Midcontinent) balancing area
- 124th of 2,383
- Plants run by Otter Tail Power Co
- 1st of 13
Operable units
| Unit | Technology | Nameplate | Summer | Online | Status |
|---|---|---|---|---|---|
| 1 | Coal steam | 450 MW | 478 MW | 1975 | Operating |
| D1 | Oil-fired | 1 MW | 1.1 MW | 1975 | Standby |
Who owns it
Shares are weighted by the nameplate capacity of each unit an owner holds.
| Owner | Share of capacity |
|---|---|
| Otter Tail Power Co | 53.9% |
| NorthWestern Energy (SD) | 23.4% |
| Montana-Dakota Utilities Co | 22.7% |
Grid and site
- Balancing area
- MISO (Midcontinent)
- Reliability region
- Midwest Reliability Organization
- Highest grid connection voltage
- 230 kV
- Water source
- Big Stone Lake
- Nearest town on record
- Big Stone City
- Operator type
- Utility
- Coordinates
- 45.304°N, 96.510°W
Closest plants
| Plant | Runs on | Capacity | Distance |
|---|---|---|---|
| State Auto Insurance | Oil and petroleum | 1.7 MW | 7.7 mi southwest |
| Valley Queen Cheese | Oil and petroleum | 4.5 MW | 8.4 mi southwest |
| Crowned Ridge Wind Energy Center | Wind | 200 MW | 18.9 mi southwest |
| Dakota Range Wind | Wind | 304 MW | 25.6 mi west |
| Dakota Range III Wind Project | Wind | 154 MW | 29.0 mi west |
| Crowned Ridge Wind II Energy Center | Wind | 201 MW | 29.0 mi southwest |
| Deuel Harvest Wind Energy LLC | Wind | 300 MW | 30.4 mi south |
| Stevens Community Medical Center | Oil and petroleum | 1 MW | 35.2 mi northeast |