Heating Guide
How Long Does a Furnace Last?
By Dioclecio Gomes, Founder & Owner3 min readUpdated October 8, 2026
In This Guide
A well-maintained furnace lasts about 15 to 20 years according to Bob Vila, and 15 to 25 years according to This Old House, with oil furnaces tending to outlast gas ones. The Department of Energy rule of thumb: if repairs would cost more than half the price of a new system, replace it. This Old House puts a new furnace at about $4,799 on average.
How long a furnace lasts depends on fuel type, maintenance and how well it was sized. The figures below come from Bob Vila, This Old House, ENERGY STAR and the Department of Energy contractor guide.
How Many Years Does a Furnace Last?
Bob Vila says a well-maintained furnace will last 15 to 20 years, with oil furnaces lasting the longest and gas furnaces the shortest. This Old House gives 15 to 25 years and notes that efficiency declines as the unit ages. Changing the filter regularly is the easiest way to protect efficiency, according to Bob Vila, along with proper venting, correct sizing and professional check-ups.
What Are the Signs a Furnace Needs Replacing?
- Energy bills climbing while fuel rates stay the same
- Uneven heating from room to room and constant thermostat changes
- A furnace over 10 years old that needs frequent repairs
Those are the warning signs Bob Vila lists. Also check the ducts: the DOE guide says duct losses can reach 30% or more when ducts are leaky, poorly insulated and run through an unheated attic or crawlspace, and a furnace's AFUE rating does not include those losses.
Should You Repair or Replace an Old Furnace?
The DOE contractor guide puts it plainly: if the cost of repairs is more than half the cost of replacement, it is better to replace with a new system than to keep repairing the old one. If the furnace is less than 15 to 20 years old and you plan to keep it, ask your contractor about improving its efficiency instead.
Thinking about a heat pump?
Heat pump installation is coming to Mr. Gomes Remodeling. Send us your details and we will reach out when we start booking in your town.
Ask About Heat PumpsHow Much Does a New Furnace Cost?
| Furnace type (This Old House, 2026) | Installed cost |
|---|---|
| All types (average) | About $4,799 |
| Electric | $2,000 to $7,000 |
| Gas | $3,800 to $10,000 |
| Oil | $6,750 to $10,000 |
ENERGY STAR says certified gas furnaces in the northern U.S. are up to 18 percent more energy efficient than baseline models and can save about $160 a year in energy costs.
Should You Replace a Furnace With a Heat Pump?
It is worth pricing both. The Department of Energy says modern air-source heat pumps can reduce electricity use by 50% compared to furnaces and baseboard heaters, and a heat pump also replaces the air conditioner. Cold-climate models on the NEEP list are built to heat at 5°F and below. See the numbers side by side in our heat pump vs. furnace cost guide, or start with the heat pump guide.
The Bottom Line
Plan on 15 to 25 years from a furnace, and replace it when repairs pass half the cost of a new system. If you are replacing anyway, price a cold-climate heat pump too. Ask About Heat Pumps
FAQ
How long does a furnace last on average?
Bob Vila says 15 to 20 years for a well-maintained furnace, and This Old House says 15 to 25 years.
Do oil or gas furnaces last longer?
Bob Vila says oil furnaces have the longest lifespan and gas furnaces the shortest.
When should I replace instead of repair my furnace?
The Department of Energy contractor guide says to replace when repairs would cost more than half the cost of a new system.
How much does it cost to replace a furnace?
This Old House puts the average at about $4,799, with electric furnaces at $2,000 to $7,000, gas at $3,800 to $10,000 and oil at $6,750 to $10,000.