You've made the decision to buy a new furnace, and your choice for fuel is gas.
The next step is to choose between two efficiency types of gas furnace -- power combustion or condensing furnaces.
Power combustion furnaces have an AFUE, or efficiency rating, of roughly 80 percent. Condensing furnaces perform better, with an AFUE of 90 percent or more. Condensing furnaces usually operate best in colder climates. Another advantage of condensing furnaces is they are not damaged by corrosion. The furnace exhausts through a plastic pipe to the outside and not through the chimney.