They're the smart ones. An annual heating system clean-and-check is one of the best home-maintenance investments you can make.

What about the 45 percent of homeowners who neglect annual maintenance? They pay the price:

• Fuel bills rise as much as 10 to 15 percent because of inefficient equipment operation. It's like having a fireplace that burns money.

• Equipment wear accelerates. Annual maintenance extends equipment life as much as 20 to 30 percent. This translates to an additional five to ten years of usage for your furnace or boiler.

• Most service contractors will tell you that about 75 percent of all repairs they do could have been avoided with regular maintenance. Heating system repairs typically run into the hundreds of dollars -- more fuel for the money-burning fireplace.

• Most important, annual heating inspections can save your life and those of your loved ones. Small cracks in a heat exchanger or problems with the flue system could allow deadly carbon monoxide gas to seep into your home. Hundreds of people in the country lose their lives each year in these tragedies. A trained service technician knows how to spot danger signs in the system.

The service technician should also clean and check (replacing if necessary) the burner, combustion chamber, heat exchanger surfaces, oil-line filter and flue pipe. Pumps and fans should be lubricated if necessary. With boilers, the technician should take time to remove sediment from boiler and steam lines, as well as checking the fan thermostat on warm air systems. Otherwise, the fan may operate longer than necessary, wasting energy.

Modern heating equipment is very sophisticated. The well-equipped service technician has an array of electronic measuring devices and tools to properly service these units.

While service is important, beyond a certain point even the best maintenance cannot save an antiquated system. Improvements in efficiency over the last few decades have been so dramatic that if your boiler or furnace is more than 20 years old, it's quite possible that it would make economic sense to replace your present system, even if it still operates fairly well. Ask a contractor to perform an energy audit of your home to see what kind of savings can be achieved by equipment replacement, and how many years it would take to pay back the initial cost of new equipment.