What describes heat rate and its calculation?

• A. The energy input per unit of electricity produced.
• B. The energy input per unit of electricity produced, typically measured as Btu per kilowatt-hour.
• C. The ratio of electricity produced to fuel energy input.
• D. The amount of steam generated per hour.

Answer: (B)

Heat rate shows how much fuel energy is needed to produce one unit of electric output. It is calculated by dividing the energy content of the fuel (fuel energy input) by the electrical energy produced (electricity output). The standard way to express it is in Btu per kilowatt-hour, so it cleanly communicates how many Btu of fuel are required for each kWh of electricity.

For example, if a plant uses 7,000,000 Btu of fuel to generate 1,000 kWh of electricity, the heat rate is 7,000 Btu/kWh. A lower heat rate means the plant is more efficient because it requires less fuel to make the same amount of electricity.

The description that specifies energy input per unit of electricity produced and uses the familiar Btu per kilowatt-hour unit matches this definition precisely. The other ideas either describe the inverse relationship (efficiency rather than heat rate) or focus on other metrics (like steam output) that aren’t about heat rate.