The best time to buy a new furnace is before you need it.
You don't want to wait till your heat conks out on a bitter day, forcing a rushed decision.
But where should you start? What should you look for?
Here's some guidance.
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DO YOU NEED ONE?
Normally, a natural-gas furnace lasts about 20 to 25 years, said Mike Foraker, president of Jennings Heating and Cooling in Akron, Ohio. But with huge improvements in efficiency, replacing an older furnace - even one that's still working well - may make economic sense.
If you have a gas furnace that's old enough to have a pilot light instead of electronic ignition, it's burning fuel constantly. Give serious consideration to replacing it, suggested Harvey Sachs, senior fellow with the nonprofit American Council for an Energy-Efficient Economy in Washington. "You're just burning dollar bills," he said.
Gas furnaces made 20 years ago are only about 70 percent efficient, meaning about 70 percent of the fuel they use is turned into heat. Today's high-efficiency furnaces are up to 96 percent efficient. That translates to a significant difference in energy costs, noted Foraker.
WHAT TO BUY?
To Sachs' way of thinking, choosing a heating system is secondary to choosing a contractor.
Over the life of a furnace or boiler, the operating costs will be many times the purchase cost, he noted. So you want to find a trustworthy, skilled contractor who will guide you to the right system for your needs.
"A smart consumer isn't concerned with the price of the furnace or boiler, but the price and value of the package the contractor is offering," he said. "...What you want is something the right size, installed properly and efficiently" in conjunction with a careful inspection of your duct work, if you have a forced-air system.
How do you find a contractor? If you've already been dealing with one you trust, that's a good choice, ACEEE says. The government's Energy Star program also suggests asking for referrals from friends and contacting trade organizations for the names of members.
ACEEE suggests looking for a contractor that employs technicians with North American Technician Excellence training or Energy Star experience. A couple of sources it recommends are natex.org or 877-420-6283, and the Web site of Air Conditioning Contractors of America, acca.org.
As always when you're hiring a contractor, ask for references and call them. It's also a good idea to check the contractor's track record with the Better Business Bureau.
WHAT CONTRACTOR SHOULD DO
Expect the contractor to do an energy survey of your home to determine how big a furnace you need.
That step is critical, Foraker said, because putting an oversize furnace into your home wastes money. "It would be like putting a V-8 engine in a small car," he said.
The survey should also determine how much heat your house is losing through cracks and openings, and where that's happening, Foraker said.
Jennings' survey typically includes a blower door test, which depressurizes the house so outside air will flow in. That makes it more easy to detect leaky spots. The survey also uses an infrared camera to spot places where heat is being lost.
The information you gain from such a survey will pinpoint leaks that need attention, so you know where to put your money in tightening up your home, Foraker said.
Doing so will mean your furnace won't need to run as long or as often to keep your house warm, saving you money. It might even be that improving your home's insulation and sealing, repairing leaky ducts and tuning up the system will be more cost-effective than replacing the furnace, ACEEE says.
A furnace's efficiency is expressed in an AFUE rating, or Annual Fuel Utilization Efficiency. The Federal Trade Commission requires all new furnaces and boilers to display an AFUE rating to help consumers compare.
For a cool to cold climate, Sachs recommends buying a furnace with an AFUE rating of at least 90 percent. Anything less is a waste of money, he contends.
If you buy a furnace with an AFUE rating higher than 90 percent, "you get some things that are nice but less essential," Sachs said.
One is a variable speed blower fan, which comes on more gradually than a typical furnace fan. It also adjusts to the conditions, saving money in electricity - as much as $150 a year, Foraker said.
Another is modulating combustion, which Sachs likens to a dimmer on a light. It allows the furnace to run at a lower capacity in milder weather.
Some furnaces pull cold air from outside instead of reheating the air that's already in the house. That allows better control of the ratio of air to gas, resulting in more efficiency, Sachs said. And since you're not drawing air from the house, you're not creating the negative pressure that pulls cold air in through all those little cracks and gaps.