Choosing a New Furnace
Photos: Keller & Keller
Richard Trethewey takes a reading of the efficiency of a furnace, the first step in determining whether it's time to replace it.
Q: I think it's time to replace my gas furnace. But before I call for estimates, can you give me some idea of what I should be looking for?

Dorothy Zalewski, Rochester Hills, Mich.

A: Richard Trethewey replies: I wish more people would think ahead like you and not wait until the dead of winter when the furnace stops working or the heating costs are sky-high. By starting to look now, you'll have a better chance of finding a good furnace you can afford. Also, heating companies aren't as busy in the summer as they'll be in the fall, so you might get a good deal on the installation.

The first step is to have someone come in to tune up your furnace, assess its condition, and determine its efficiency. You'll need that number and some old fuel bills to be able to calculate how much you can save with a new unit. The other key number—in addition to the price tag of a new furnace—is its AFUE, or annual fuel utilization efficiency. The higher the AFUE, the lower your monthly heating costs. Then go to and plug those numbers into its online calculator. You'll be able to see your potential savings and how long it will take before your investment in the furnace breaks even.

But owning a new, efficient furnace isn't the whole story, and it may not even be the most important part. A furnace has to be sized properly for your home and installed correctly by a capable, experienced company. Otherwise you won't see the fuel savings you expect.

And don't forget about the less sexy side of heating home improvement. If the air ducts are leaky, your insulation is minimal, and the weatherstripping around doors and windows is letting all that very expensive warm air leak into the neighborhood, your nice new furnace will be little better than a shiny new car with a hole in the gas tank.
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