AFUE
Annualized Fuel Utilization Efficiency (AFUE): The AFUE is the measure of efficiency for furnaces on a 0 to 100 scale with 100 being the best performance possible. A point on the scale equals 1% of efficiency; therefore an 80 AFUE furnace is 80% efficient. A 78 AFUE is the government minimum and 97 AFUE is the current high rating.