Compare Gas Furnace Prices, Repair Installation Costs. Gas furnaces are one of the most popular, effective, and cost efficient ways to heat your home during the winter months..See price comparisons on popular gas furnacends..Gas Furnace Installation Cost and Extras. How much does it cost to install a gas furnace? The answer depends on the variables that affect installation cost..Based on the costs of gas it has been found that the gas furnace is typi.y the cheapest and most efficient. It is always recommended to get three estimates before deciding which furnace and installation a homeowner chooses to go with..