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Furnaces are the most commonly used residential heating system in the United States. Furnaces can be fueled by natural gas, oil, propane, coal, wood or electricity, but most use natural gas, oil and electricity and deliver their heat through a duct system. One in four furnaces in U.S. homes today is more than 20 years old.

The efficiency of new furnaces is measured by the Annual Fuel Utilization Efficiency (AFUE), a rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 AFUE means that approximately 90 percent of the fuel is utilized to provide warmth to a home, while the remaining 10 percent escapes as exhaust. Furnaces today are between 78% AFUE and 96% AFUE. The AFUE is typically listed on the unit’s yellow “Energy Guide” label.

Find performance certified furnaces.