An 80% efficient, natural gas furnace offers greater energy savings and improved comfort over an older, less efficient natural gas heating system. An 80% efficient, two-stage furnace with enhanced blower may reduce your energy cost by up to 25%. These heating units are best in mild winter climates. These gas furnaces are are easily converted to propane gas heating with the addition of a propane conversion kit. Choose from Fedders, Ruud and Goodman natural gas furnace prices. Select from upflow, downflow, or horizontal configurations.