Capacity factor
The ratio of the energy a power plant actually produces over a period to the energy it would produce running at full nameplate capacity for the whole period.
Capacity factor is the most widely used measure of how hard a generating asset works. It applies to every technology, from nuclear reactors to rooftop solar, and is usually quoted on an annual basis.
A 100 MW wind farm producing 350 GWh in a year has CF = 350,000 / (100 × 8,760) = 40%. The same number expressed in hours is the plant's full-load hours (3,504 h).
Typical annual values (IRENA Renewable Power Generation Costs, NREL ATB, EIA):
- Nuclear: 80–93% (US fleet above 90% in recent years, EIA)
- Geothermal: 70–90%
- Offshore wind: 35–50% for new North Sea projects
- Onshore wind: 25–45%, global new-build weighted average around 36–39%
- Hydropower: 30–60%, strongly dependent on hydrology and dispatch role
- Utility solar PV: 10–30%; fixed-tilt in central Europe about 11–13%, single-axis tracking in deserts 25–30%
- Gas peakers (OCGT): often below 15%, by economic choice rather than technical limit
Capacity factor reflects both the resource and the plant's role. A low value for a dispatchable plant usually means it is run only at peak prices; for variable renewables it mostly reflects weather, curtailment and design choices such as the DC/AC ratio. It feeds directly into the denominator of LCOE: halving the capacity factor roughly doubles the capital share of cost per MWh.
Related terms
All terms →- Full-load hours
The number of hours per year a plant would need to run at rated power to deliver its actual annual output; equal to capacity factor multiplied by 8,760.
- LCOE (Levelized Cost of Electricity)
The constant price per MWh that recovers all lifetime costs of a power plant, discounted to present value, divided by its discounted lifetime output.
- Capacity credit
The fraction of a resource’s nameplate capacity that can be counted on to meet peak demand, used in adequacy planning and capacity markets.
- Curtailment
Deliberate reduction of a generator’s output below what it could produce, usually wind or solar, because of grid, market or system constraints.
- Load factor
The ratio of average demand to peak demand over a period, indicating how evenly a consumer or system uses electricity.
- Specific yield
Annual energy produced per unit of installed PV capacity, expressed in kWh/kWp per year; combines solar resource and system performance.