The most efficient gas furnace is about 95%. The actual furnace price depends on the Btu capacity you select. High efficiency gas furnace pricing will be higher but long term energy savings are maximized and year-end tax credits eliminate any price advantage of lower efficiency systems. A new 95% efficient gas furnace offers 16% energy savings over an 80% efficient furnace. Choose from Fedders, Ruud and Goodman gas furnace price options