Afue Ratings Explained

Homeowners in our chilly region should know all about the efficiency of their heating systems. If you have a furnace or boiler, that means understanding AFUE ratings. AFUE (annual fuel utilization efficiency) ratings tell you how efficient a heating system is. By law, AFUE ratings are displayed on new furnaces and boilers so that consumers can compare them. The higher the AFUE, the more efficient the system, and the more you’ll save on heating bills.

What AFUE Means

AFUE is a measurement signifying how efficient a heating system is as it converts energy throughout the year. Your older furnace, for example, may have an AFUE of only 80 percent. This means only 80 percent of the energy turns into heat for the home, while the other 20 percent goes up the chimney. AFUE ratings don’t take into account additional heat losses when conditioned air travels through ductwork or pipes located in unconditioned spaces. These losses may be as high as 35 percent.

AFUE rates combustion-powered as well as electric heating systems. Since an electric furnace does not require a flue, it has no flue loss, so AFUE ratings are very high, between 95-100 percent. 

Modern furnaces are more efficient because of consumer demand as well as legislation designed to protect the environment.. Since 1992, new residential furnaces are required to have an AFUE of 78 percent, but most newer furnaces achieve an AFUE of 80 percent or more. 

New Technology

Technological innovations in furnace manufacture result in ever higher AFUEs. Condensing furnaces, with sealed combustion chambers and a second heat exchanger, typically have AFUEs of 90-98.5 percent.

To learn more about AFUE, contact Efficient Heating and Air Conditioning. We serve Spearfish, SD and the Northern Black Hills.