Grid Reliability
Sources with high capacity factors can supply steady baseload power, while sources with lower capacity factors typically need backup generation or storage.
In plain English
How hard a power plant actually works.
It measures how much of the time a power plant is actually cranking out electricity at full strength. A higher number means the plant runs closer to round-the-clock.
Simple example
According to the U.S. Energy Information Administration, U.S. nuclear plants had an average capacity factor of about 93% in recent years, compared with roughly 25% for solar and 35% for wind.
Why it matters
What the term actually changes.
Cost Comparisons
Capacity factor affects the true cost per unit of electricity, complicating simple comparisons between nuclear, natural gas, wind and solar.
How it works
The mechanics, in practice.
Simple Formula
Actual electricity generated is divided by the maximum possible output over the same period, such as a year, to produce the percentage.
What Lowers It
Refueling outages, maintenance, weather, fuel availability and demand fluctuations all reduce a plant's capacity factor below 100%.
Related guide
Should the U.S. expand nuclear power to address climate change?
Nuclear energy supplies nearly half of America's carbon-free electricity, but expanding it raises questions about cost, safety and waste.
Read the guide → Related issue brief
Should the U.S. Expand Nuclear Power to Address Climate Change?
As the country seeks to cut greenhouse gas emissions, policymakers are divided over whether to build more nuclear reactors or focus on other low-carbon options.
Read the brief →You’ve learned the term. Now vote.
Should the United States expand nuclear power to address climate change?
Live results — 186 voters
Anonymous · one vote per person