Capacity factor is the percentage of a power plant's maximum output that it actually produces over time. A nuclear plant with a 93% capacity factor runs nearly all the time. Solar panels have capacity factors around 20-25% because they only generate during daylight. Wind turbines average 25-45% depending on location. Capacity factor is critical for comparing different energy sources and understanding the true cost and reliability of generation assets.
Capacity Factor
The ratio of actual electricity output to maximum possible output over a period, measuring plant efficiency.
Related Terms
Base Load
The minimum level of electricity demand over a 24-hour period, typically supplied by always-on power plants.
Generation Mix
The combination of energy sources (coal, gas, nuclear, renewables) used to produce a state's electricity.
Megawatt (MW)
A unit of power equal to one million watts, used to measure the capacity of power plants.
this entity is one of the U.S. state-level electricity rates and generation mix concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the EIA Open Data API and State Electricity Profiles data behind every per-entity page on the site.
In the the EIA Open Data API and State Electricity Profiles data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.
Source: U.S. Energy Information Administration, 2026.