Acronyms of Efficiency

AFUE - Annual Fuel Utilization Efficiency-the standard measurement of efficiency for gas and oil-fired furnaces. Given in percentages, this number tells you how much of your fuel is being wasted. The higher the AFUE, the greater the efficiency. If a furnace has an AFUE of 80%, for every $1.00 worth of fuel, $0.80 of it is turned into heat, the other $0.20 is wasted (it's expelled as flue gas).

HSPF - Heating Seasonal Performance Factor-the efficiency measurement used to gauge the efficiency of the heating mode of heat pumps. The greater the number, the greater the efficiency of the unit. The HSPF can be thought of as the "averaged factor" for an entire heating season. HSPF can be calculated by taking the total annual heating requirements, including all energy inputs (defrost and back-up heat energy included) divided by the total electric power used.

SEER - Seasonal Energy Efficiency Ratio-the measure of efficiency by which the cooling process of air conditioners and heat pumps is rated. The higher the SEER number, the greater the efficiency, which yields greater energy savings. The SEER is defined as the total cooling output (in British thermal units or Btu) provided by the unit during it's normal annual usage period divided by it's total energy input (in watt-hours) during the same period.