MILLSTONE
OperatingNuclear power plant
- Capacity
- 2,163 MW
- Primary fuel
- Nuclear
- County
- Southeastern Connecticut Planning Region
- Operator
- DOMINION NUCLEAR CONN INC
- Status
- Operating
- Commissioned
- 1975
- EIA plant ID
- 566
- Generators
- 2
- Technology
- Nuclear
- Net generation (2024)
- 16,870 GWh
- Capacity factor (2024, EIA nameplate)
- 85%
- Data vintage
- EIA-860 2024 final; EIA-923 2022-2024 final
- Coordinates
- 41.3115, -72.1678
MILLSTONE, a 2,163 MW Nuclear power plant in Southeastern Connecticut Planning Region, Connecticut. Operated by DOMINION NUCLEAR CONN INC, commissioned 1975.
How MILLSTONE compares
With 2,163 MW of capacity, MILLSTONE is the largest of the 68 operating power plants Bywatts maps in Connecticut. It accounts for about 23% of all operating capacity in Connecticut. Nationally it is the 19th-largest of the 55 operating Nuclear plants in the database. Commissioned in 1975, it is older than 71% of the 66 operating Connecticut plants with a recorded commissioning year. It shares Southeastern Connecticut Planning Region with 19 other operating plants, including MONTVILLE STATION and PFIZER GROTON PLANT.
EIA-860 lists 2 generators at the site with 2,260 MW of nameplate capacity, all nuclear technology. Net generation was 16,870 GWh in 2024 (an 85% capacity factor), up 2% from 2022. Its generators came online between 1975 and 1986.
Grid neighborhood
The nearest named substation is FLANDERS, about 4.6 miles away; the closest transmission line found within 10 miles is a 345 kV line, under 0.1 miles away. Another 23 operating power plants totaling 768 MW sit within 25 miles; the largest is MONTVILLE STATION (495 MW, Oil).
Computed by Bywatts from HIFLD power plant, substation and transmission line records and EIA-860/923 survey data; distances are straight-line. Sources and methodology
Weather peril exposure
MILLSTONE is a 2,163 MW nuclear power plant in Southeastern Connecticut Planning Region, CT, operated by DOMINION NUCLEAR CONN INC, commissioned in 1975. Southeastern Connecticut Planning Region carries moderate modeled catastrophe exposure in the FEMA National Risk Index, scoring 2.1 of 5 at the 28th national percentile. Hurricane is the leading peril, rated Relatively High by FEMA at the 87th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a nuclear plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Southeastern Connecticut Planning Region hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Hurricane | Relatively High | 87th | 4.5 of 5 | 0.19 |
| Coastal flooding | Relatively Moderate | 60th | 3.4 of 5 | 3.7 |
| Riverine flooding | Relatively Moderate | 58th | 3.3 of 5 | 2.3 |
| Earthquake | Relatively Low | 52nd | 3.1 of 5 | <0.01 |
| Ice storm | Relatively Moderate | 41st | 2.6 of 5 | 1.7 |
| Wildfire | Very Low | 22nd | 1.9 of 5 | <0.01 |
| Tornado | Relatively Low | 21st | 1.8 of 5 | 0.16 |
| Winter weather | Relatively Moderate | 20th | 1.8 of 5 | 13.3 |
| Lightning | Relatively Moderate | 11th | 1.4 of 5 | 23.2 |
| Strong wind | Relatively Moderate | 10th | 1.4 of 5 | 1.6 |
| Heat wave | Relatively Low | 6th | 1.2 of 5 | 4.5 |
| Hail | Relatively Low | 2nd | 1.1 of 5 | 1.7 |
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.