AFUE
annual fuel utilization efficiency
AFUE (annual fuel utilization efficiency) is the federal rating of how much of a furnace's fuel becomes heat for the home over a year, including standby and off modes; an 80% AFUE furnace turns 80% of its fuel into delivered heat.
DOE’s energy conservation standards for consumer furnaces are expressed in AFUE, which it describes as an annualized fuel efficiency metric that accounts for fossil fuel use in active, standby and off modes. The test procedure is in 10 CFR part 430, subpart B, appendix N.
Under a 2007 rule, non-weatherized gas furnaces made on or after November 19, 2015 must reach at least 80% AFUE; weatherized gas furnaces 81%, and non-weatherized oil furnaces 82%. Condensing furnaces, which recover heat from the exhaust with a second heat exchanger, reach 95% and above; DOE’s 2023 rule notes through-the-wall models rated above 96%.
AFUE is a fraction of fuel, while a heat pump’s coefficient of performance compares heat with electricity and can exceed 1. To compare running costs, divide each energy price by its efficiency for the same amount of delivered heat.
Sources
Last updated