Afternoon Feast: AFUE
Annual Fuel Utilization Efficiency for Homeowners and Home Inspectors
Annual fuel-utilization efficiency (AFUE):
A measure of how efficiently a gas or oil furnace or boiler converts fuel into usable space heat over the course of a typical year. AFUE is expressed as a percentage—for example, an AFUE of 80% means that 80% of the fuel's energy is used to heat the home, while the remaining 20% is lost, typically through the flue or other system inefficiencies. AFUE ratings are established through standardized testing procedures developed by the U.S. Department of Energy.
Note for inspectors: AFUE ratings are often found on the appliance’s nameplate or manufacturer’s label and can help assess the relative efficiency of older versus newer heating systems. While not required to measure or verify AFUE, inspectors can use this rating as a contextual indicator of equipment performance and potential energy costs.