Question: Re: glossary could you please explain what the AFUE is? Answer: annual fuel utilization efficiency The AFUE rating is a measure of how much of each dollar's worth of fuel burned by your appliance goes toward heating your home. Electric heat (radiant) is nearly 100% efficient since there is no chimney loss. Stoves, however, do put some heat and some unburnt fuel up the chimney. This is all figured into the AFUE.