Last updated on November 22nd, 2019
Let’s evaluate our capacity factor definition and a few examples of capacity factor in practical use case scenarios.
What is the Capacity Factor?
Capacity factor is the primary determinant of the number of times a power plant can run for a particular period. It is expressed as a percentage and is usually calculated by dividing the actual electrical energy output over a given period by the maximum possible electrical energy output over the same period.
The capacity factor is usually expressed as the ratio of the average power generated over a period compared with its maximum output. It is not always possible to tell the exact amount of electricity produced by a particular energy source by merely checking the size or the nameplate capacity of a power plant.
The capacity factor is calculated as follows:
Capacity factor = Average energy output over a specified period kWh/maximum output over that period kWh (100)
Capacity Factor Definition and Examples
The capacity factor varies according to the electricity producing system and the fuel type, for example, It can either be power plants consuming fuel to generate electricity or power plant using renewable energy sources including solar, wind or geothermal among others.
Example of Capacity Factor for Solar Power
To complement the capacity factor definition, let’s look at a practical example:
The common timeframe for analysis is either a month with 30 days or 720 hours or a year with 8760 hours.
Here is an example (just for illustrative purposes):
If a 100-kW solar power system produces 20,530 kWh in a month, the capacity factor is calculated as follows:
Capacity Factor = 20,530/72,000 (100) = 28.51%
According to the U.S capacity factors, solar power capacity factor is usually smaller compared to the capacity factors of other sources of energy such as coal power plants. However, solar power has an extra benefit since it operates with a free input from the sun and does not emit carbon to the environment.
To be able to compare power plants based on their capacity factor, they must have the same generation technology and fuel type or the renewable energy source.
Capacity Factors by Renewable Energy Resource
Capacity factors by form of generation varies depending on a number of factors. Here is a breakdown of capacity factors by renewable energy resource:
- Hydropower: 30-40% factor of capacity
- Solar: 15-26% factor of capacity
- Solar Thermal: 15-35% factor of capacity
- Landfill Gas: 65-75% factor of capacity
- Biomass: 50-60% factor of capacity
- Geothermal: 70-80% factor of capacity
This should give you a good understanding of what plants can produce power at optimal levels throughout the day.
Benefits of the Capacity Factor Measure
There are a number of benefits to consider as to why capacity factor is an appropriate measure for a power system’s performance.
- It indicates how fully a unit’s capacity is utilized
- It measures the value of a power plant
- It represents how close a renewable source turbine operates to the ideal output
See more of our other green living and renewable energy definitions to learn more.
What do you consider to be your favorite metric for renewable energy power plant resources? Did our capacity factor definition help you? Let us know. We’d love to hear from you.
Green Coast is a renewable energy blog community that will help you learn about renewables, energy efficiency and green living.« Back to Glossary Index