All of the gas furnace prices shown here are for 95% efficient, single stage units. A gas furnace cost analysis has shown these to be a great bargain, with long term energy savings maximized while 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 prices.