Sizewell B — United Kingdom

Sizewell B is a 1,250 MW nuclear power station in England, United Kingdom. It is operated by British Energy (now part of EDF). Based on reported annual generation of 7,417 GWh, it can supply roughly 2.1 million homes. It ranks #37 of 2,860 United Kingdom power plants by installed capacity. Commissioned in 1966, it is around 60 years old — an older, legacy facility. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, nuclear supplies about 12.4% of United Kingdom's electricity; the national grid averages 217 gCO₂/kWh (64.4% low-carbon) (2025).

Plant data: WRI Global Power Plant Database (CC BY 4.0), id GBR1000058.

Data provenance

Source of the capacity and fuel values:

capacity: GEM · 2026 · L100000500378; fuel: WRI GPPD

In context: how this plant compares

At 1,250 MW, Sizewell B is well above the median nuclear plant in United Kingdom (965 MW). Technically it is described as gas-cooled reactor. 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

68%, from 7,417 GWh of reported generation

Share of United Kingdom nuclear capacity

4.5% of 27,683 MW across 25 plants in this dataset

Age among peers

9 of 16 dated nuclear plants in United Kingdom are older

Calculated from the capacity and generation records in this dataset (WRI Global Power Plant Database (CC BY 4.0)).

Capacity vs largest nuclear plants in United Kingdom

Installed capacity (MW), WRI Global Power Plant Database (CC BY 4.0).

Owner

Operated by British Energy (now part of EDF).

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 52.2°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 21% 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: 62/100 — 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 corrosive environment (estimated ISO 9223 class C4 — High), 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 #7 largest nuclear power plant of 25 in United Kingdom by capacity.

United Kingdom has 25 nuclear power plants in this dataset, together about 27,683 MW of capacity.

Nearby power plants

• Reydon Farm (resubmission) · Solar · 3.9 MW · England
• Parham Airfield (Great Glenham) · Solar · 17.5 MW · England
• Bentwaters Park (extension) · Biomass · 1.8 MW · England
• Bentwaters Park · Biomass · 2 MW · England
• Bentwaters CHP · Biomass · 4.6 MW · England
• Holton Airfield · Solar · 11 MW · England

Location

Coordinates 52.2145, 1.6206 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.

Frequently asked questions