Gas furnaces offer significantly better energy efficiency than fireplaces and oil-fueled furnaces. Gas-fueled boilers provide even better efficiency, but are typically more expensive than gas furnaces.
Furnaces use fans to transfer air throughout a structure, while boilers use pipes that radiate heat through a room. The process of heating air and blowing it leads to efficiency losses. However, the difference in efficiency can be minimal, and homeowners with existing furnace infrastructure may find the lower cost of furnaces to be a better option.
Gas furnaces are more efficient than comparable oil-fueled furnaces. This, combined with the low cost of natural gas, makes it the most popular domestic heating option as of February 2015.