Capacity Factor
Capacity factor (CF) is the ratio of a power plant's actual energy output over a period of time to its maximum possible output if it operated at full rated capacity continuously. It is expressed as a percentage and is a key performance metric for all electricity generation technologies.
Capacity Factor = Actual Output (kWh) ÷ (Rated Capacity (kW) × 8,760 hours/year)
For a 100 kW solar PV system that produces 160,000 kWh in a year:
CF = 160,000 ÷ (100 × 8,760) = 18.3%
Typical Solar PV Capacity Factors
Solar PV capacity factors range widely depending on location and system configuration:
- US Southwest (fixed-tilt): 22–28%
- US Southeast (fixed-tilt): 18–22%
- US Midwest/Northeast (fixed-tilt): 14–18%
- Single-axis tracking, US Southwest: 28–35%
- Germany (fixed-tilt): 10–13%
Utility-scale solar with single-axis tracking typically achieves 5–8% higher capacity factors than fixed-tilt arrays at the same location due to morning and afternoon tracking improvements.
Capacity Factor vs. Other Technologies
Comparing capacity factors across generation technologies helps contextualize solar's intermittency:
- Nuclear: 90–95%
- Natural gas (combined cycle): 50–60%
- Wind: 30–45%
- Solar PV: 15–30%
Lower solar capacity factors are offset by near-zero fuel costs and minimal variable O&M expenses, making solar cost-competitive despite its intermittent nature.
In SolarScope
SolarScope calculates and displays the estimated capacity factor for your project based on the system size, location irradiance, and performance parameters.