How Long Does a Furnace Last? Lifespan and Warning Signs

Short answer

A gas furnace typically lasts 15 to 20 years, and a well-maintained one can go longer. ENERGY STAR suggests weighing a replacement once a furnace passes 15 years, and the U.S. Department of Energy's 2023 furnace rule assumes an average life of 21.5 years. Electric furnaces often last 20 to 30 years, according to Carrier and Lennox.

Age alone is not a reason to replace. Frequent repairs, rising bills, a yellow burner flame, soot, or a carbon monoxide alarm are the signs that matter.

How long furnaces last, by source

There is no single official number. The main sources cluster around 15 to 20 years for a gas furnace, and the Department of Energy's own furnace analysis uses a longer average.

Furnace lifespan estimates by source

Bars are ranges and squares are single figures. Sources: ENERGY STAR; NAHB and Bank of America Home Equity (2007); InterNACHI; ASHRAE equipment life chart; U.S. Department of Energy, 2023 furnace rule; Carrier, Lennox, and Bryant.

What each figure measures. ENERGY STAR's number is a checkpoint, not a lifespan.
Source	Figure	What it measures
ENERGY STAR	More than 15 years	Age at which to start weighing a replacement
NAHB and Bank of America Home Equity (2007)	15 to 20 years; gas 18, electric 15, oil 20	Average life for the first owner
InterNACHI	15 to 25 years	Estimated service life used by home inspectors
ASHRAE equipment life chart	18 years	Median life, gas or oil furnace
U.S. Department of Energy (2023 rule)	21.5 years	Average life assumed in its gas furnace analysis
Carrier, Lennox, Bryant	Gas 15 to 20 years; electric 20 to 30	Manufacturer guidance

The sources split on electric furnaces. The 2007 NAHB study, which drew on appliance industry data from 2005, lists electric furnaces at 15 years, shorter than gas. Carrier and Lennox put them at 20 to 30 years and Bryant says up to 30, because an electric furnace has no burners, no combustion, and fewer moving parts. The manufacturer figures are newer; the NAHB number is worth knowing as the low end.

Furnaces in western Washington

Our winters are long and mild rather than harsh. NOAA's 1991 to 2020 normals put Sea-Tac Airport at 4,376 heating degree days a year and the Tacoma station at 4,332. Chicago O'Hare logs 5,974 and Minneapolis 7,399. Heating degree days measure how much heating a climate asks for, so a Tacoma furnace does roughly 73% of the heating work of one in Chicago.

Annual heating degree days, 1991 to 2020 normals

Base 65°F. Source: NOAA National Centers for Environmental Information, U.S. climate normals 1991 to 2020.

Less total work does not guarantee a longer life. The local trade-off is damp air: Sea-Tac averages 39.34 inches of precipitation a year, and Lennox notes that excess moisture in or around a furnace leads to corrosion. If your furnace sits in a garage or crawlspace, keep an eye out for rust on the cabinet and the flue pipe.

Local homes are getting older, too. The Census Bureau's 2020 to 2024 American Community Survey puts the median year built at 1987 for Puyallup and 1986 for Pierce County, so the original furnace in a typical home here would be well past every figure above. Gas heat is common but not the majority:

Share of occupied homes by main heating fuel. Source: U.S. Census Bureau, ACS 2020 to 2024 5-year estimates, table B25040. "All other fuels" is the remainder.
Main heating fuel	Pierce County	Puyallup
Electricity (heat pumps, electric furnaces, baseboard)	59.9%	57.0%
Utility gas	33.8%	40.2%
All other fuels	6.3%	2.8%

What shortens a furnace's life

Dirty filters. ENERGY STAR warns that a dirty filter can damage equipment and lead to early failure, and it recommends checking the filter monthly.
The wrong size. The Department of Energy notes that an oversized system cycles on and off too often. Lennox lists oversizing, dirty filters, thermostat placement, a dirty flame sensor, and a clogged flue as causes of short cycling, which shortens furnace life.
Overheating. Trane names wear and tear, overheating, an oversized furnace, and rust as the causes of cracked heat exchangers, and Lennox points to restricted airflow as a cause of overheating.
Moisture. Water in or around the cabinet leads to corrosion.
Venting problems. The Consumer Product Safety Commission's inspection guidance covers chimneys and flues for blockages, corrosion, and partial or complete disconnections.
Installation shortcuts. Carrier counts professional installation, correct sizing, and well-designed, sealed ductwork among the factors that decide how long a furnace lasts.

Much of that is settled on install day. That is why we treat proper sizing, sealed ducts, and correct airflow as part of every install: those details decide whether a system makes it past 15 years.

Signs a furnace is near the end

It is more than 15 years old, ENERGY STAR's checkpoint for weighing a replacement.
Repairs keep coming and energy bills keep climbing.
Some rooms run too hot or too cold, or the house has new humidity or dust problems.
The furnace has gotten louder, bangs or rattles, or shuts off and restarts in short bursts.
The burner flame is yellow, orange, or flickering instead of a steady blue.
There is soot around the furnace, rust on the flue pipe, or a strong metallic smell.
A carbon monoxide alarm has gone off.

The last three can point to a cracked heat exchanger or a venting problem, and they need a technician right away. Trane's guidance for a cracked heat exchanger is to replace the heat exchanger or the whole furnace rather than try to repair the crack.

If a CO alarm sounds or you smell gas

For a carbon monoxide alarm, the Consumer Product Safety Commission says to move outside to fresh air right away, call 911 or your fire department, and stay out until responders say it is safe to go back in. The Washington State Department of Health lists early CO symptoms as headache, dizziness, fatigue, weakness, confusion, and nausea.

If you smell gas, Puget Sound Energy says to leave first, then call 911 and PSE at 1-888-225-5773.

Washington law, RCW 19.27.530, requires carbon monoxide alarms in residential buildings, with an exception for owner-occupied single-family homes lived in before July 26, 2009. When a home is sold, the seller has to install them before the buyer moves in. CPSC recommends an alarm on every level of the home and outside sleeping areas, and not in the kitchen or directly above a fuel-burning appliance.

Repair or replace

We would rather fix a furnace that has good years left than sell you one you do not need. When a repair quote gives you pause, two rules of thumb help frame it.

Trane's $5,000 rule multiplies the furnace's age by the repair cost; above $5,000, start pricing a replacement. The 50 percent rule, which both Lennox and Trane describe, says a repair that costs about half of a new furnace or more is usually better spent on the new one.

Example figures to show how the $5,000 rule works. It frames the decision; it does not make it.
Furnace age	Repair quote	Age × quote	The rule suggests
5 years	$350	$1,750	Repair
10 years	$450	$4,500	Repair, and start planning
15 years	$600	$9,000	Price a replacement
20 years	$300	$6,000	Price a replacement

The rule misses things. A failed part on a young furnace may be covered by the parts warranty, and a cracked heat exchanger on an old one usually ends the conversation. For the price side, see our furnace replacement cost guide for Pierce County. If your furnace is acting up, book a furnace repair visit and we will tell you whether the repair is worth it.

Check the warranty before you decide

Before you pay for a major part, check whether it is still covered. Terms vary by model, and registration is what most often decides the length of coverage.

Sources: manufacturer warranty pages. Terms vary by model and change over time; your warranty certificate governs.
Brand	Heat exchanger	Parts	Register within
Carrier (Comfort 96, 59SC6)	Lifetime limited with timely registration; 20 years otherwise	10 years parts, or 5 years parts plus 3 years labor; 5 years parts if not registered	90 days
Trane	20 years, registered or not	10 years if registered; 5 years if not	60 days
Goodman	Lifetime limited	10 years if registered; 5 years if not	60 days

Keep the install date and registration confirmation with your home records. If you are buying a house, ask the seller for both.

How to get more years out of a furnace

Check the filter every month during heating season, change it when it looks dirty, and change it at least every three months (ENERGY STAR).
Have the system inspected every fall. CPSC and the EPA both recommend a yearly professional inspection of fuel-burning heating systems, including the flue.
Keep the area around the furnace clear and dry, and keep furniture off the return vents.
Put CO alarms on every level of the home.
When it is time to replace, size the new furnace to the house, not to the old unit's label.

Our maintenance plans include a fall heating tune-up and a spring cooling tune-up. If a heat pump shares the work with your furnace, our heat pump maintenance checklist covers the outdoor unit.

Frequently asked questions

How long does a gas furnace last?

Most gas furnaces last 15 to 20 years. The NAHB life expectancy study lists gas furnaces at 18 years, and the U.S. Department of Energy uses a 21.5 year average in its furnace analysis. Maintenance, sizing, and installation quality decide where a given furnace lands.

Is it worth repairing a 20-year-old furnace?

Sometimes, for a small repair. Trane's $5,000 rule multiplies age by repair cost, so a $300 repair on a 20-year-old furnace scores $6,000, which points toward pricing a replacement. A cracked heat exchanger at that age usually means a new furnace.

How long do electric furnaces last?

Carrier and Lennox put electric furnaces at 20 to 30 years because they have no burners or combustion. The older NAHB study lists 15 years, so treat 20 to 30 as the high end for a well-kept unit.

Does annual maintenance make a furnace last longer?

It deals with the causes of early wear. ENERGY STAR warns that a dirty filter can damage equipment and lead to early failure, and the Consumer Product Safety Commission recommends a professional inspection every year to catch venting and heat exchanger problems.

Are carbon monoxide alarms required in Washington homes?

Washington law (RCW 19.27.530) requires carbon monoxide alarms in residential buildings, except owner-occupied single-family homes occupied before July 26, 2009. Sellers must install them before a buyer moves in. CPSC recommends one on every level and outside sleeping areas.

What are the signs a furnace needs to be replaced?

Age past 15 years, frequent repairs, rising energy bills, uneven heating, new noises, a yellow or flickering burner flame, soot, rust on the flue, or a carbon monoxide alarm. The flame, soot, and alarm signs need a technician right away.

Not sure your furnace has more years in it?

Dennis inspects furnaces across Puyallup, South Hill, Tacoma, and the rest of Pierce County and tells you straight whether a repair is worth it. Read more about furnace repair in Puyallup.

Request service Call (253) 254-2145

Sources 29 sources, click to expand

ENERGY STAR, When to replace heating and cooling equipment.
ENERGY STAR, Maintenance checklist.
ENERGY STAR, Heating and cooling.
NAHB and Bank of America Home Equity, Study of life expectancy of home components (copy hosted by a third party) (February 2007).
InterNACHI, Standard estimated life expectancy chart.
ASHRAE, Equipment life expectancy chart (copy hosted by a third party).
Federal Register, Energy conservation standards for consumer furnaces, final rule (88 FR 87502) (December 18, 2023).
Carrier, Electric vs. gas vs. oil furnace.
Bryant, How long does a furnace last?.
Carrier, How long does a furnace last?.
NOAA National Centers for Environmental Information, U.S. climate normals 1991 to 2020, annual and seasonal (Seattle-Tacoma, Tacoma #1, Chicago O'Hare, Minneapolis-St. Paul) (accessed September 15, 2026).
U.S. Census Bureau, American Community Survey 2020 to 2024 5-year estimates, table B25035 (median year structure built).
U.S. Census Bureau, American Community Survey 2020 to 2024 5-year estimates, table B25040 (house heating fuel).
U.S. Department of Energy, Building America, Proper sizing of HVAC systems.
Lennox, Furnace short cycling (April 4, 2025).
Lennox, Furnace cracked heat exchanger (November 24, 2025).
Trane, Cracked heat exchanger.
Minnesota Department of Health, Carbon monoxide (updated August 18, 2026).
U.S. Consumer Product Safety Commission, Carbon monoxide fact sheet.
U.S. Consumer Product Safety Commission, Carbon monoxide questions and answers.
U.S. EPA, Carbon monoxide's impact on indoor air quality (updated July 15, 2026).
Washington State Department of Health, Carbon monoxide.
Puget Sound Energy, Natural gas safety.
Washington State Legislature, RCW 19.27.530, carbon monoxide alarms.
Trane, Should you repair or replace your heating and cooling system? (modified February 2, 2026).
Trane, Repair or replace (June 18, 2026).
Carrier, Comfort 96 gas furnace (59SC6).
Trane, Trane warranties explained (modified September 16, 2025).
Goodman, The gas furnace warranty: the why, when, and how.