Shop our selection of Forced Air Furnaces in the BTU Multi Position Multi S.d Gas Furnace that maximizes energy usage to minimize utility costs..Replacing a gas furnace can cost $ $, for a self contained and vented wall unit that provides air directly to the surroundinge $ $, for a gas floor furnace heat rises from a grill flush with the floor $, $, for a mid efficiency gas furnace in a central heating system and $, $, or more for a .For a basic project in zip code furnace, the cost to Install a Gas Furnace starts at $, $, per furnace. Actual costs will depend on job size, conditions, size options. To estimate costs for your project . Set Project Zip Code Enter the Zip Code for the location where labor is hired and materials purchased. ..Comparison Guide to Gas Furnace Prices, Installation Costs, Furnace Repair Costs and Much More..