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Capacity factor

Capacity factor is how much electricity a plant actually produced, as a share of what it could have produced running at full power the whole time.

Also called CF, net capacity factor

Formula

Capacity factor = net generation (MWh) ÷ (capacity (MW) × hours)

Net generation
Electricity delivered in the period after the plant's own use, in MWh
Capacity
The rated output in MW, on the same basis for the whole period
Hours
Hours in the period: 8,760 in a normal year and 8,784 in a leap year

With real numbersVogtle, 2025: 37,144,415 MWh ÷ (4,658 MW × 8,760 h) = 91.0%

In the data

87.8%Nuclear fleet capacity factor in 2025, the highest of any fuel

Nuclear ran at 87.8% of its capacity in 2025. Solar ran at 23.0%, because the sun sets, not because the panels are inefficient.

Capacity factor by fuel, 2025
87.8%Nuclear48.6%Coal38.3%Gas36.9%Hydro33.9%Wind23.0%Solar

EIA-923 net generation and EIA-860 capacity, 2025. Single-fuel projects with all 12 months reported, weighted by capacity.On the map

Built from InfraMap's 2025 data with the same tools the analyst uses.

Common mistakes

  1. Reading a low capacity factor as a bad plant. Solar at 23% is normal because the sun sets. Capacity factor says nothing about efficiency or breakdowns.
  2. Treating capacity factor as dependable capacity. A wind farm at 35% does not supply 35% of its rating when demand peaks. That takes a reliability study.
  3. Averaging plant percentages. For a group, add the MWh and divide by the total MW-hours, so a large plant counts for more than a small one.
  4. Comparing a partial year with a full one, or dividing by today's capacity for a year when the plant was smaller.

How the InfraMap analyst defines it

Actual electrical output relative to output possible at the specified capacity over the period. It does not measure conversion efficiency, availability or firm capacity.

CF = net MWh / sum of compatible capacity MW times elapsed hours

Reviewed October 1, 2026 against the references below. The analyst and the MCP server answer with this definition.

Primary references

See it for any US plant