Millstone — United States of America
Nuclear power plant in Connecticut, United States of America. Approximate location 41.3107, -72.1677.
NuclearConnecticutUnited States of America
Millstone is a 2,198 MW nuclear power station in Connecticut, United States of America. It is operated by Dominion Energy Nuclear Conn Inc. Based on reported annual generation of 16,733 GWh, it can supply roughly 4.8 million homes. It ranks #149 of 10,884 United States of America power plants by installed capacity. Commissioned in 1981, it is around 45 years old — long-established. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, nuclear supplies about 17.4% of United States of America's electricity; the national grid averages 384 gCO₂/kWh (43.0% low-carbon) (2025).
Plant data: WRI Global Power Plant Database (CC BY 4.0), id USA0000566.
Data status
Known data
Calculated from dataset
Not available
Known, modelled and calculated values are kept separate. Missing fields are shown as unavailable.
Data provenance
Source of the capacity and fuel values:
capacity: GEM Global Nuclear Power Tracker September 2025 operating-unit sum (location L100000500045); fuel: WRI GPPD
In context: how this plant compares
At 2,198 MW, Millstone is well above the median nuclear plant in United States of America (1,350 MW). Nuclear plants split uranium to raise steam with no direct CO₂; they run as steady baseload with very high capacity factors and the longest operating lifetimes of any thermal plant.
Capacity comparison computed from the WRI Global Power Plant Database; fuel-type context is general engineering background.
Key facts
- Load factor
- 87%, from 16,733 GWh of reported generation; the median for 57 nuclear plants in United States of America that report generation is 89%
- Generation trend
- 17,080 GWh in 2013 and 16,733 GWh in 2019 (−2%)
- Highest and lowest year
- 2015: 17,411 GWh; 2014: 15,841 GWh
- Share of United States of America nuclear capacity
- 0.8% of 270,415 MW across 176 plants in this dataset
- Age among peers
- 60 of 111 dated nuclear plants in United States of America are older
Calculated from the capacity and generation records in this dataset (WRI Global Power Plant Database (CC BY 4.0)).
Reported generation trend
Annual generation (GWh), WRI Global Power Plant Database (CC BY 4.0).
Owner
Operated by Dominion Energy Nuclear Conn Inc.
Local climate & thermal context
This nuclear plant uses heat from nuclear fission to raise steam for a turbine-generator. It sits in a temperate oceanic climate (Köppen Cfb) — Northern Hemisphere, latitude 41.3°N — which shapes how much energy it can produce and how its output varies through the year.
Monthly mean temperature
Heating degree-days here run 24% above the median power plant in this dataset — a proxy for how much extra energy heated equipment must replace through its surfaces in winter.
Climate heat-demand index: 64/100 — this site sits in the mid third of the power plants we cover by heating degree-days.
Climate normals: WorldClim 2.1 (1970–2000 monthly normals, 10 arc-min, CC BY 4.0); zone: Köppen-Geiger world climate classification (Kottek et al. 2006, 0.5° grid). Degree-days & heat-demand index computed by PowerAtlas — a modelled heat-demand proxy, not a measured site figure.
Site climate & environmental severity
This site sits in a moderately corrosive environment (estimated ISO 9223 class C3 — Medium), with humidity / wetness the leading environmental stress.
Indicative estimate via the ISO 9223:2012 informative method (atmospheric corrosivity from temperature, time-of-wetness and airborne salinity), using WorldClim climate normals, the Köppen-Geiger class and coast distance. Indicative, not a measured corrosion rate.
How it compares & nearby plants
The #59 largest nuclear power plant of 176 in United States of America by capacity.
United States of America has 176 nuclear power plants in this dataset, together about 270,415 MW of capacity.
Nearby power plants
- Pfizer Groton Plant · Gas · 37.5 MW · Connecticut
- Pfizer Groton Fuel Cell · Gas · 5.6 MW · Connecticut
- Bridge Street 1 & 2 · Oil · 5.2 MW · Connecticut
- CMEEC - Polaris Park Solar Hybrid · Solar · 3.5 MW · Connecticut
- Water Treatment 1 & 2 · Oil · 5.2 MW · Connecticut
- CMEEC - Navy NE Trident · Solar · 1 MW · Connecticut
Location
Coordinates 41.3107, -72.1677 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.
Frequently asked questions
What type of power plant is Millstone?
Millstone is a 2,198 MW nuclear power plant in Connecticut, United States of America, commissioned in 1981.
How much electricity does Millstone generate?
Millstone generates about 16,733 GWh of electricity per year.
Who operates Millstone?
Millstone is operated by Dominion Energy Nuclear Conn Inc.