(From Consumer Reports, December 2012)

Consumer Reports ComparisonGas furnaces you can count on

Dreading a furnace replacement? Today’s more-efficient gas furnaces can save you around $17 for every $100 you spend on fuel compared with older models. They are also, on average, less likely to need repairs, according to our survey. But you might want to think twice about gas furnaces from York, which broke down almost twice as often as other brands.

That’s what subscribers told us about 32,251 furnaces they bought between 2007 and early 2012. Reliability is especially important because when a furnace failed, 75 percent needed significant work. A majority of those broke down completely, with nearly a third producing no heat for more than a day. For 38 percent, the repair cost was $150 or more.

If a key part such as the heat exchanger or control module fails, you’re better off replacing the furnace if it’s more than about 15 years old. Otherwise, repairing rather than replacing a furnace might make more sense. If your furnace is on the fritz, try the following before you call a contractor or start shopping:

Check the filter. If you’re getting low airflow, check the air filter on the furnace. A clogged filter could cut airflow down to a trickle. The top-rated 3M Filtrete Elite Allergen 2200MPR, $24, traps dust better than the usual furnace filter, so it can also help clean the air. Check it monthly and replace when dirty.

Inspect electrical parts. Loose wires or a thermostat malfunction could also cause heat problems. If your thermostat runs on batteries, try changing them. And make sure that burned-out fuses or tripped breakers haven’t shut power to the fan or circuit board.

Every home with a gas or oil furnace should have a CO alarm on each floor and near (not inside) an attached garage. One we recommend is the First Alert CO615, $40. Test the alarm weekly, vacuum it monthly and replace it every five years. Don’t remember how old the alarm is? Look on the back for the manufacture date.

Click here to download a PDF of the report.