HVAC

How Often Should You Service Your Furnace?

Furnaces rarely fail without warning — they fail after years of small problems nobody looked at. One visit a year, before the cold arrives, catches most of them.

The short answer

Have your furnace professionally serviced once a year, ideally in early fall before you need the heat. That applies to gas, oil, and propane furnaces alike; oil-fired systems burn dirtier and genuinely need the annual cleaning. If you have a heat pump that heats and cools, aim for twice a year — once before summer, once before winter — since it works in both seasons.

Why an annual service is worth it

Three reasons, in order of importance. Safety: a fuel-burning furnace produces carbon monoxide, and a cracked heat exchanger, blocked flue, or poorly adjusted burner can let it into your home — a technician checks for exactly that. Reliability: most mid-winter breakdowns trace back to parts that were visibly wearing out months earlier, like a failing igniter or a dirty flame sensor. Coverage: many manufacturer warranties require proof of annual professional maintenance, so skipping it can void the coverage on an expensive part.

Efficiency matters too. A furnace with dirty burners, a clogged filter, or a struggling blower runs longer to deliver the same heat — and you pay for every extra minute.

What a proper tune-up includes

• Inspecting the heat exchanger for cracks or corrosion.
• Checking the flue and venting for blockages, leaks, and proper draft.
• Testing for carbon monoxide around the furnace and at the vents.
• Cleaning and adjusting the burners, and checking the flame.
• Cleaning the flame sensor and testing the igniter or pilot.
• Checking the blower motor, belt (on older units), and wiring connections.
• Testing the safety controls and limit switches, and verifying the thermostat cycles the system correctly.
• Clearing the condensate drain on high-efficiency furnaces.

Expect roughly an hour and, in most areas, somewhere in the range of $100 to $200. Many HVAC companies offer a yearly maintenance plan that bundles the visit with priority scheduling — worth considering if you'd rather not think about it at all.

Signs it needs attention now

• Your carbon-monoxide alarm sounds, or people in the home get headaches, dizziness, or nausea that ease when they leave. Get everyone outside and call your gas utility or 911 first — not a service appointment.
• A yellow or flickering burner flame instead of a steady blue one.
• The furnace cycles on and off frequently, or runs constantly without warming the house.
• Banging, squealing, or rattling noises when it starts or runs.
• Some rooms are noticeably colder than others, or airflow from the vents feels weak.
• Heating bills climbing faster than your usage or energy rates explain.
• Soot around the furnace or registers, or excess moisture on windows during heating season.

What you can do between visits

1. 1Check the filter monthly during heating season and replace it when it looks dirty — this is the single biggest thing you control.
2. 2Keep at least 2 to 3 feet around the furnace clear of boxes, laundry, and anything flammable.
3. 3Make sure supply vents and return grilles aren't blocked by furniture or rugs.
4. 4On a high-efficiency furnace, keep the outdoor intake and exhaust pipes clear of snow, leaves, and nests.
5. 5Test your carbon-monoxide and smoke alarms, and replace the thermostat batteries if it uses them.

Make it automatic

The annual service is easy to put off because nothing forces the date. Add your furnace to Upkeepery and it schedules the yearly tune-up and the monthly filter checks, reminds you before the fall rush, and keeps a record of every visit — handy for warranty claims and for the next technician who asks when it was last serviced.