To save you from seeing your breath billow inside your home this winter, now is the time to get your furnace inspected and serviced.

There are those who wait until snow is on the ground before they think about their heating systems. By then, they have to suffer behind other cold callers.

Dirt and neglect are the top causes of furnace failure, according to the Environmental Protection Agency, so each home needs an annual checkup.

"It ensures the performance is what it should be to get through the season before you need to use it," said Chandler von Schrader, program analyst for the EPA's Energy Star home improvement team in Washington.

That means hiring the right heating and cooling contractor. Plan to spend $90 for each inspection. Contractors also offer maintenance agreements that include heating and cooling checkups, which typically lower the price to $70 for each inspection. Be wary of companies that offer services for $50 or lower because they might be cutting corners, energy experts say.

Look for companies that offer a multiple-part inspection. Neal Harris Heating, Air Conditioning and Plumbing in Kansas City, Mo., has a 16-point checkup, which includes examining electrical wiring, cleaning the system and looking for cracked parts that leak deadly carbon monoxide.

"We find those all the time," said Ryan Parshall, a spokesman for Neal Harris. "Contractors are in the business of saving lives in addition to making homes comfortable."

Residents also can keep their furnaces working properly by doing their own routine maintenance, von Schrader said. Here's what to do:

* Change air filters monthly. A clogged filter hurts the blower motor, which starves the system of air. Energy Star experts recommend filters with a Minimal Efficiency Report Value rating of six or above.

* Buy a programmable thermostat. They can save about $100 a year on heating and cooling bills, and wear and tear on the furnace. They cost between $50 and $120.

* Tighten the duct system. Ducts are inherently leaky, but those deficient ducts can reduce a system's efficiency by 20 percent and cause uneven heating. Look for dirt streaks on ductwork. Where you see them, air is slipping out. Seal duct leaks with duct mastic or metal-backed tape, but not duct tape -- it's not strong enough on its own.

* Seal cracks. Caulk or weather-strip gaps in your home. The attic and basement are where most are found. You also may want to add insulation.

If you need a new furnace, call a contractor.

It might be time to replace your system if it's 15 years or older or hasn't been properly maintained. Sinking $500 into an 18-year-old furnace is like putting a new transmission in a beater car.

A new standard 80 percent-efficient furnace costs $2,000 to $3,000. Add between $1,500 and $2,000 for a 90 percent-efficient, Energy Star-qualified system. The higher performing system reduces heating bills between 30 percent and 40 percent each year. These costs can vary considerably by region.

One-fourth of the homes that contractors see have undersized or oversized furnaces, Parshall said.

Contractors gauge heat loads before replacing furnaces. Having an undersized furnace won't get the job done. And having an oversized one will cost more, unevenly heat a home and cause wear and tear on the system.

Maintenance Check List

According to Energy Star, at the very least, your heating contractor should:

* Check thermostat settings to ensure that the heating system turns on and off at the right temperatures.

* Tighten all electrical connections and measure voltage and current on motors.

* Lubricate all moving parts.

* Inspect the condensation drain in your furnace.

* Check system controls to ensure safe operation.

* Show you how to correctly change your air filter.

* Check all gas or oil connections, gas pressure, burner combustion and heat exchanger.

Hiring a Contractor

According to Energy Star and North American Technician Excellence, before you have your furnace inspected or a new system installed, you should:

* Know the model of your current system and its maintenance history, and make note of any uncomfortable rooms. This will help potential contractors better understand your heating needs.

* Consider professionals certified by North American Technician Excellence (NATE), the leading industry-supported testing and certification program. Call 877-420-6283 or 703-276-7247; visit their Web site at www.natex.org.

* Ask for a copy of proof of insurance and liability.

* Call a contractor's references.

* Get at least three written, itemized estimates for major work. When studying bids, be sure to compare cost, energy efficiency and warranties. An inexpensive furnace may not be the best deal. If it's not efficient, your energy costs will be higher.

* Sign a written proposal with a contractor before work starts. It will protect you by specifying project costs, model numbers, job schedule and warranty information.