In a natural gas or propane furnace, a pilot light ignites the source gas, igniting burners inside a combustion chamber. The generated heat then enters a heat exchanger, transferring heat to the air and raising the temperature of a space to the level set by a thermostat.
Furnaces are rated by the Annual Fuel Utilization Efficiency (AFUE) ratio, which is the percent of heat produced for every dollar of fuel consumed. Lennox offers residential furnaces with AFUE ratings ranging from the federal minimum of 80% all the way up to an industry-leading 98.7%. The most efficient models can save you hundreds of dollars a year, compared to an older or less-efficient furnace.
