How to Calculate a Boiler AFUE

Boilers heat water and provide either hot water or steam to heat homes and industrial facilities.

Boilers are used in home and industrial complexesBoilers are used in home and industrial complexes
The hot water or steam is distributed through heating ducts, coils or radiators. The boiler annual fuel utilization efficiency, or AFUE, is the ratio of heat output of the boiler to the total energy used by the boiler. In general, it measures how efficiently boilers use energy. The Federal Trade Commission (FTC) requires boiler manufacturers to display their AFUE rating so customers can compare options when shopping.

Calculate the heat output of the furnace or boiler. Get this number from the boiler specification sheet or by contacting the manufacturer. As an example, assume it's 45 British Thermal Units (BTUs) per hour.

Locate the total energy used by a boiler. Get this number from the boiler specification sheet or by contacting the manufacturer. Assume it's 60 BTUs per hour.

Calculate the AFUE by dividing the heat output of the boiler by the total energy used by the boiler. Using the example numbers, the AFUE is 75 percent: 45/60

Things You Will Need

  • Boiler specifications

About the Author

Dwight Chestnut has been a freelance business researcher and article writer for over 18 years. He has published several business articles online and written several business ebooks. Chestnut holds a bachelor's degree in electrical engineering from the University of Mississippi (1980) and a Master of Business Administration from University of Phoenix (2004).