How is energy use and efficiency measured?
The efficiency of gas and oil furnaces is measured in a rating known as AFUE (Annual Fuel Utilization Efficiency). A lot like your car’s miles per gallon rating, AFUE tells you how efficiently the furnace converts fuel (gas or oil) into heat. An AFUE of 90% means that 90% of the fuel is used to heat your home, while the other 10% basically goes up the chimney. In 1992, the U.S. government established a minimum AFUE rating for furnaces installed in new homes at 78%. (In contrast, many furnaces manufactured before 1992 had AFUE ratings as low as 60%; – so nearly half the fuel was being wasted.) Furnaces with AFUE ratings of 78% to 80% are considered “mid- efficiency”; those with ratings of 90% or higher are known as “high-efficiency.” The maximum furnace efficiency available is around 96.6%. The cooling efficiency for air conditioners and heat pumps is measured in a rating known as SEER (Seasonal Energy Efficiency Ratio). The higher the number, the greater the efficiency. The typical SEE
