Capacity Factor Calculator

Capacity Factor is defined against the full period -- Hours in Period times Rated Capacity -- not against only the hours the generator was actually available, which is a deliberate industry convention: it measures output against a fixed, comparable theoretical ceiling. Planned Downtime only enters the Availability and Availability- Adjusted CF calculations instead.

Capacity Factor divides Actual Production by the maximum possible output over the entire period, downtime included. Availability-Adjusted CF divides the same Actual Production by the maximum possible output over only the hours the unit was actually available, excluding downtime -- so for identical production, Availability-Adjusted CF will always read higher whenever Planned Downtime is greater than zero (and up to the period length).

Up to a point. Holding Actual Production fixed, excluding more hours from the denominator while the numerator stays the same mechanically increases the ratio -- a generator making the same energy in fewer available hours performed better against its own achievable ceiling. But the effect runs away as available hours approach zero: a period with only a handful of available hours will report a ratio in the hundreds or thousands of percent, which is an artefact of the arithmetic, not a real performance reading. Downtime is capped at the length of the period, and once it reaches the full period there are no available hours left and Availability-Adjusted CF is reported as zero rather than as an undefined division.

It's Actual Production divided by Rated Capacity -- the number of hours the generator would have needed to run at 100% of its nameplate rating to produce the same total energy. It's a common way in the wind and solar industry to express annual output without needing to state the capacity factor percentage directly.

EIA's Electric Power Monthly reports annual US fleet capacity factors of roughly 33-36% for wind (33.5% in 2023, an eight-year low, against 35.9% in 2022, the all-time high) and about 23-25% for utility-scale solar PV. Individual projects vary widely -- recently-built land-based wind projects average nearer 40%, and the newest US offshore wind farms have reported figures in the high 40s and low 50s over their first year of operation. Fossil generation is not the 90%-plus benchmark it is often assumed to be: EIA puts the US coal steam fleet at 48.7% and combined-cycle gas at 58.4% for 2025. Nuclear is the only fleet consistently above 90% (91.0% in 2025). Treat all of these as rough sanity checks against your own result, not targets.