Enter the thermal energy input and the electric energy output into the calculator to determine the heat rate.

Heat Rate (Efficiency) Formula

The following equation is used to calculate the Heat Rate (Efficiency).

HR = TEI / EEO * 100
  • Where HR is the heat rate efficiency (%)
  • TEI is the thermal energy input
  • EEO is the electrical energy output

To calculate the heat rate efficiency, divide the thermal energy input by the electrical energy output.

What is Heat Rate (Efficiency)?


Heat Rate efficiency is a measure of how much energy is required to keep the steam turbine at its operating temperature. Nuclear plants have high heat rates, meaning that they need a lot of energy to operate. Coal plants have low heat rates, which means they don’t need as much energy to run. This makes coal plants more cost-effective than nuclear plants, even though coal plants are more expensive to build.

Heat rate efficiency is an important factor when comparing the cost of different kinds of generating units for power plants. In an integrated power grid where fuels are derived from different sources (nuclear, coal, natural gas) heat rates are also useful for determining the most efficient fuel mix as well as which generators will be needed to balance load at any given time.

Heat rate efficiency also measures thermal power plant in relation to the amount of coal or other fossil fuels consumed for each kilowatt hour of energy produced. Heat rate efficiency results are expressed as Btu/kWh, or MMBtu/MWh (British thermal units per kilowatt hour).