Heating Repair Guides

Which heating system do you have?

Most homes heat with one of three systems, and each one moves heat in its own way. A furnace runs on gas, oil, propane or electricity and delivers its heat through a duct system.⁠[1] A boiler burns gas, propane or oil to heat water or steam. That water or steam circulates through radiators, baseboards or radiant floors, and a boiler uses no ducts.⁠[1]

A heat pump does not burn fuel. It moves heat, pulling it from outdoor air into the house in winter and out of the house in summer.⁠[2] Because it moves heat instead of making it, a heat pump can deliver up to three times more heat energy than the electricity it uses.⁠[2] A central heat pump can use the ducts already in the house. Ductless mini-splits mount indoor units on a wall or ceiling and need no ducts at all.⁠[2]

Telling the three apart is quick. Warm air from floor or ceiling registers means a furnace or a ducted heat pump. Hot radiators or baseboards with no air blowing mean a boiler. A heat pump also has an outdoor unit that keeps running in cold weather. If your outdoor unit only runs in summer, it is an air conditioner, and your heat most likely comes from a furnace.

Heating safety basics

If you smell gas, follow the emergency steps at the top of this page. They match the NFPA gas message for central heating: if you smell gas, do not light the appliance, leave and call for help.⁠[3] Never relight a furnace or boiler while you can still smell gas.

Fuel-burning heaters must vent their exhaust outdoors. Fuel that burns incompletely makes carbon monoxide, which can cause illness and death.⁠[3] Keep the vent outlet clear of snow, ice and debris, and install CO alarms inside the home.⁠[3] Keep anything that can burn at least 3 feet away from heating equipment.⁠[3]

The guides on this site stop at checks and simple upkeep an owner can do safely. Gas valves, gas lines, venting and heat exchangers go to a licensed technician. Heat pumps add one more limit. Federal rules prohibit intentionally venting refrigerants and their substitutes, such as HFCs, during service or disposal.⁠[4] Technicians who service equipment that could release ozone-depleting refrigerants must be EPA-certified.⁠[5]

Common heating problems and the first check

Furnaces, most of them gas-fired, are the most common home heating system in the United States, so most guides start there.⁠[1] Use the first check in each row before you call for service.

Gas furnace owners can go further on the furnace problems page, which shows the parts inside the cabinet and the start-up sequence step by step.

Yearly upkeep for any heating system

Keep the filter clean. ENERGY STAR says to check a furnace or heat pump filter every month. Change it when it is dirty, or at least every three months.⁠[1] For heat pumps, it adds that filters should be cleaned when they look dirty or when the filter light comes on.⁠[2]

Have every heating system serviced once a year. NFPA says heating equipment and chimneys should be cleaned and inspected every year by a licensed professional.⁠[3] The U.S. Department of Energy says a regular maintenance schedule can cut heating and cooling costs by 10% or more and help the equipment last longer.⁠[8] It suggests a furnace check in the fall.⁠[8] Heat pump owners should also clear weeds and debris from around the outdoor unit so air can move freely.⁠[8]

Use the thermostat to save energy. DOE says you can save 1% on heating bills for each degree you set the thermostat back over an eight-hour period.⁠[8]

Know roughly how much life is left. A 2007 NAHB study gives furnaces 15 to 20 years, heat pumps 16 years and boilers 13 to 21 years.⁠[9] ENERGY STAR suggests weighing a replacement when a furnace or boiler is more than 15 years old, or a heat pump more than 10.⁠[7] Frequent repairs, rising bills, rooms that stay too hot or too cold and a noisy system are other signs it lists.⁠[7]