Enter the net useful electric output, the net useful thermal output, and the total fuel energy input into the calculator to determine the CHP efficiency.

CHP Efficiency Formula

The following equation is used to calculate the efficiency of a CHP system.

CHP = (We + Qo) / Qi
  • Where CHP is the combined heat and power efficiency.
  • We is the net useful electric output of the CHP
  • Qo is the net useful thermal output of the CHP
  • Qi is the total fuel energy input of the CHP

To calculate the CHP efficiency, add together the useful electrical and thermal outputs of the system, then divide by the total fuel energy input.

What is CHP?


CHP, short for combined heating and power, is a term used to describe any system that provide both a useful thermal output and a useful power output, in the form of electricity.

How to calculate CHP efficiency?

Example Problem:

The following example outlines the steps and information required to calculate the efficiency of a combined heating and power system.

First, determine the useful thermal output. In this example, the useful thermal output is 500 Joules.

Next, determine the useful electrical output. In this case, the electrical output is 400 Joules.

Next, determine the total energy input of the fuel. For this system, the fuel provides 1000 Joules of energy.

Finally, calculate the CHP efficiency using the formula above:

CHPe = (We + Qo) / Qi

CHPe = (500 + 400) / 1000

CHPe = .90 = 90%