Deciding between a gas furnace or an electric furnace unit is a common dilemma. Many homeowners are tempted by the cleanliness and the relative safety of an electric furnace unit. A gas furnace unit, though, has many benefits. They have higher energy efficiency and a longer life span than do electric furnaces. Electric furnace units are more expensive to purchase, although they are easier and cheaper to install. As far as operating costs though, the gas furnace units are less expensive than the electric ones. Gas furnaces do have a risk, albeit very small, of explosion and carbon monoxide poisoning. Those risks can be reduced by properly maintaining the furnace unit, however.