Written October 2026, at the start of heating season, with this year’s prices and rebates.
A gas furnace lasts 15 to 20 years. That’s the range Trane, Carrier and Lennox each publish, and it’s the answer we’d give you standing next to yours. Sized right and looked after, plenty go past 20. Oversized, choked by dirty filters and never checked, some are done at 12. When yours is done, a new gas furnace runs $4,285 to $14,040 installed from us, by size and efficiency. From about $71 a month at 0% APR for 60 months, the whole price financed, on approved credit.
The number matters less than the timing, and it’s heating season. A worn-out furnace rarely quits on a mild afternoon. It quits on the first hard cold night, when it runs the longest and every furnace on the street is being asked to do the same. ENERGY STAR’s own advice is to have the heat checked in the fall, because contractors get busy once winter comes. If yours is 15 or older, now is when to find out what shape it’s in.
Furnace lifespan at a glance
| The question | The short answer |
|---|---|
| Average furnace lifespan | 15 to 20 years for a gas furnace. Trane, Carrier and Lennox all publish that range. |
| 80% vs 95% gas furnace | The same 15 to 20 years; none of the three gives them different numbers. A 95% adds parts that handle water, and that’s where a neglected one fails. |
| Electric furnace | 20 to 30 years, by Lennox’s and Carrier’s numbers. |
| Trane, Carrier, Lennox | 15 to 20 years on average. Trane says a well-kept Trane can pass 20; Carrier says a high-quality furnace can reach 30. |
| How old is too old | Past 15, ENERGY STAR says start looking at a replacement. Age alone doesn’t end a furnace; a cracked heat exchanger or a big repair bill does. |
| What wears one out early | Oversizing and short cycling, dirty filters, water where it shouldn’t be, a careless install. |
| What stretches it | A heating check every fall and a filter checked every month in winter. |
| How long a replacement takes | One working day for most. New venting or ductwork can add more. |
How long does a furnace last, really?
Ask the companies that build them and you get the same answer three times. Trane: “The average furnace will last 15-20 years.” Carrier: most residential furnaces last 15 to 20 years. Lennox: 15 to 20 years with proper care. All three name the same things that decide where in that range yours lands: whether it was sized and installed right, how hard it works, and whether anyone looks at it once a year.
Some do a lot better. Trane says a well-maintained Trane furnace can last 20 years or more, and Carrier says a high-quality furnace “can potentially last up to 30 years.” Electric furnaces run longer still, 20 to 30 years by Lennox’s and Carrier’s numbers. If yours burns natural gas or propane, plan around 15 to 20.
Weather plays a part too. Trane puts it simply: the longer the winters and the harder the furnace works, the shorter its life. Northern Virginia winters are real but short next to the upper Midwest’s, so here the install and the upkeep move the number more than the weather does.
80% vs 95%: does a high-efficiency furnace last as long?
The percentage is AFUE, the share of the gas’s heat that ends up in your house over a year. An 80% furnace loses about a fifth of it, mostly out the vent. A 95% furnace adds a second heat exchanger that pulls so much heat out of the exhaust that the water in it condenses. That’s why a 95% vents through PVC pipe and needs a condensate drain: the white pipe and the little pump in the video above.
None of the makers gives a 95% a shorter or longer life than an 80%. What changes is how it fails. Carrier warns that “improper drainage in high efficiency furnaces can lead to internal damage,” and Lennox’s installation manual says the drain line belongs inside the heated part of the house “to avoid freezing of condensate and blockage of drain line.” Lennox also says the flue gas may be acidic. Drained and vented right, a 95% lasts like any furnace. With a sagging drain line running through a cold garage, it won’t.
We’d still pick a 95% for most houses here: less gas burned every winter, and Washington Gas pays money back on the good ones (the numbers are in the cost section below). An 80% still makes sense where there’s no reasonable way to run the PVC and a drain from where the furnace sits.
How long does a Trane, Carrier or Lennox furnace last?
On the makers’ own numbers, about the same: 15 to 20 years on average. The differences are in what they promise around it. Trane says a well-maintained Trane can pass 20, credits its stainless steel heat exchangers, hot surface igniters and gaskets, and warranties the heat exchanger for 20 years to the life of the furnace, depending on the model. Carrier says a high-quality furnace can reach 30. Lennox says one with annual maintenance “should easily last over 15 years.”
The badge matters less than you’d think. A top-line furnace that’s oversized and short cycling can wear out before a basic one sized right. We’re a Trane Comfort Specialist, Carrier experts and a Rheem Pro Partner, and we service every major brand, so take this from people who sell all of them: judge the installer as hard as the brand. Our furnace brand ranking goes model by model.
What wears a furnace out early in Northern Virginia
Four things, roughly in the order we find them.
It’s too big for the house. An oversized furnace heats the air near the thermostat in a few minutes, shuts off, and starts again. Carrier says systems that are too large “will turn on and off rapidly,” and that those short cycles stress the parts toward early failure. Trane says a furnace wears out early whether it’s oversized or undersized, and Lennox lists oversized, short-cycling furnaces among the causes of cracked heat exchangers. We see it on replacements all the time: the old furnace was sized as “whatever was there, plus a little.” Why a furnace short cycles, and what size your house actually needs.
It can’t breathe. A packed filter starves the furnace of air, and the heat that should leave with that air stays in the metal. ENERGY STAR says a dirty filter “can increase energy costs and damage your equipment, leading to early failure.” Lennox ties dirty filters and restricted airflow to overheating, and overheating to cracked heat exchangers. ENERGY STAR’s numbers: check the filter every month in winter and change it at least every three months. Sooner with pets or dust from a renovation. Which filter, and how often.
Water where it shouldn’t be. Two places. On a 95% furnace it’s the condensate drain: if that line runs through a garage, a crawlspace or out a wall, a cold snap can freeze it, and the furnace shuts itself off on the coldest night of the year. Lennox’s manual says the line belongs in the heated space, or under a heat cable where it can’t be. The other is the air conditioner coil sitting on top of the furnace: when its drain pan clogs, it drips on the furnace below, and Lennox names rust from excess moisture as a cause of heat exchanger cracks. The drain that shuts your furnace off.
A careless install. Trane says it plainly: “Sloppy installation can shorten the life of your furnace and ductwork.” Gas pressure, airflow, venting and the drain all get set on install day. Lennox’s manual warns that failing to set the temperature rise, how much the furnace warms the air passing through it, “may cause erratic limit operation,” which is the furnace overheating and shutting itself down. A furnace can leave the factory perfect and be shortchanged in its first afternoon.
What makes a furnace last longer: a heating check every fall
The cheapest years you’ll ever add to a furnace come from one visit a year. Trane says a furnace with a yearly inspection will generally last longer than one without. Lennox says annual maintenance should easily carry one past 15. The Consumer Product Safety Commission says to have the heating system “professionally inspected and serviced annually.” And ENERGY STAR’s list of what that visit covers is the list that matters for a gas furnace: the gas connections, gas pressure, burner combustion and the heat exchanger.
Ours is the heating check: $67 per system, through December 31. We check your furnace or heat pump before the cold gets here, and anything we find comes with its price in writing before any work. If the blower wheel is caked with dust, the same page has the deeper cleaning. See the heating check, everything we’re running right now, or what a full furnace tune-up includes and costs.
One more that helps more than people expect: a heat pump in front of the furnace. Trane says a heat pump may help a furnace last longer, because it carries the heat on milder days and saves the gas furnace for the cold ones. How dual fuel works here.
Signs your furnace is going out
Any one of these is worth a look. Two or three together, on a furnace past 15, and it’s time to put a replacement price next to the repair price.
- It’s past 15. ENERGY STAR’s first sign it’s time to replace is a furnace or boiler “more than 15 years old.” The date is on the label inside the furnace door.
- The repairs keep coming. ENERGY STAR and Carrier both flag frequent repairs, and Lennox says multiple repairs within a few years reveal a furnace that’s failing.
- The gas bill climbs with no change in how you live or what the gas company charges. ENERGY STAR and Trane both list it.
- Rooms that won’t warm up, or a furnace that can’t hold the thermostat setting on a cold night.
- New noises. Trane: “Loud banging, booming, or grinding noises are not normal.” What each furnace sound means.
- Cold air from the vents, or a furnace that lights and shuts off a few seconds later. That one is often a dirty flame sensor, a small fix. How to tell.
- Short cycles, rust or soot around the furnace or its flue pipe, or a burning or chemical smell. Lennox lists every one of those as a sign of a cracked heat exchanger, which is next.
If the heat is out right now, start with what to check and how to stay warm tonight.
Cracked heat exchanger and carbon monoxide
The heat exchanger is the metal wall between the flame and the air your furnace blows through the house. Lennox describes it as the part that moves heat from the combustion gases into your air while its walls keep gases like carbon monoxide out, and says a crack “can allow carbon monoxide (CO)” into the home. The causes it names line up with everything above: age and metal fatigue, dirty filters and restricted airflow that overheat it, oversized and short-cycling furnaces, and rust from moisture. ENERGY STAR adds that a cracked heat exchanger makes the burner run less safely.
That’s why the heat exchanger is on our heating check. Lennox’s view on a crack: because it’s a sealed part, “repairs are rarely recommended.” The exchanger gets replaced, or the whole furnace does, and on an older furnace we’d put the money into the furnace. How to know a cracked heat exchanger diagnosis is real.
Whatever the furnace’s age, have working CO alarms. The Consumer Product Safety Commission says to put battery-operated or battery-backup CO alarms on every level of the home and outside sleeping areas. Its symptom list: headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion. If you suspect CO poisoning, CPSC says to get outside to fresh air immediately, then call 911. What to do if your carbon monoxide alarm is going off.
Repair or replace an old furnace?
Here’s how we’d think it through, with our own price book.
A small part, any age: repair it. A flame sensor cleaned is $95 to $180. An igniter is $240 to $410. Those are the most common no-heat calls we run in the fall, and neither is a reason to buy a furnace.
A big part on a furnace past 15: get the replacement price first. A control board is $550 to $1,180 and a blower motor is $670 to $2,400. Lennox’s rule of thumb is to replace when a repair costs more than half of a new furnace. We’d add age to that: on a furnace near 20, even a repair well under half buys a couple of winters, not ten. Carrier says replacing a 20-year-old furnace “is often the smart financial move.”
A cracked heat exchanger on an older furnace: replace it. Lennox says patching one is rarely recommended: the fix is a new heat exchanger or a new furnace. On a furnace past its heat exchanger warranty, the new furnace is usually the better spend.
A repair visit starts with the diagnostic, $99, and you get the problem and the price in writing before any work. If the honest answer is replace, we’ll say so. If it’s “this one has years left,” we’ll say that too. Furnace repair prices, fix by fix.
How old is too old for a furnace?
There’s no birthday that condemns a furnace. ENERGY STAR’s line is 15 years: past that, start pricing a replacement, and Carrier says the same. What actually ends a furnace is a cracked heat exchanger, a repair bill that’s a big share of a new one, or small repairs that won’t stop. A 22-year-old furnace that passes its check every fall can keep going. A 13-year-old one that’s oversized and short cycling may not see 15.
If the air conditioner is about as old as the furnace, Trane’s advice is to consider replacing it at the same time. It’s one install day instead of two, and the second row of the price table below is that job.
What a new furnace costs in Northern Virginia
Straight from our price book, the same one our furnace estimator runs on. The spread is size and efficiency: a small, basic furnace at the bottom, a big high-efficiency one at the top.
| Job | Monthly, from | Installed, our price book |
|---|---|---|
| A new gas furnace (keeping your air conditioner) | From $71 a month | $4,285 to $14,040 |
| Furnace and air conditioner together | From $148 a month | $8,898 to $23,000 |
Monthly figures: 60mo @ 0% APR on each starting price, the whole price financed, on approved credit. Longer plans lower the payment and cost more in total. The lender sets the final terms.
These ranges cover every brand, size and efficiency we install, not one model, and your price comes in writing before anything is decided. Get the price for your house in a couple of minutes with our furnace estimator. Financing is on approved credit (how it works).
Money back from Washington Gas. If Washington Gas is your gas company, it pays $500 back on a new ENERGY STAR furnace rated 95.1% to 96.9% AFUE, and $700 on one rated 97% or better. It has to be installed by one of its participating contractors, and we’re in Washington Gas’s contractor network for furnaces. The paperwork is due within 30 days of the install, and the money runs while program funds last. A furnace installed in 2026 gets no federal tax credit (what’s left). Whatever we’re running right now is on our offers page.
How long does it take to install a furnace?
One working day for most replacements. The crew covers the floors, the old furnace comes out, the new one goes in, and the gas, power, venting and ductwork get connected and tested. Plan on the heat being off for most of the day. In most houses it’s back by evening.
It takes longer when the job changes something. Going from an 80% furnace to a 95% means new PVC venting and a condensate drain, the same extras the Department of Energy counts for a condensing replacement. A furnace of a different size or shape can need new sheet metal to meet the old ducts. A tight closet or an attic slows everything down. A good estimate tells you which of these apply before the day starts. And the last hour matters as much as the tear-out: gas pressure, the temperature rise and the safety controls, checked with the furnace running.
The best time to replace a tired furnace is before it fails, when you pick the day. In January, the day picks you. What actually happens on install day.
Furnace lifespan questions people ask us
How long do furnaces last on average?
15 to 20 years for a gas furnace. That’s the range Trane, Carrier and Lennox all publish. A well-kept one can pass 20; an oversized one that never sees a clean filter can be done at 12.
How long does a gas furnace last?
15 to 20 years, natural gas or propane. Sizing, the install and a yearly check decide which end of that you get. We install and service both.
Does a 95% furnace last as long as an 80%?
As far as the makers say, yes: Trane, Carrier and Lennox don’t give them different lifespans. A 95% has a condensate drain and PVC venting that an 80% doesn’t, and a drain that clogs or freezes is how a neglected one fails.
How old is too old for a furnace?
ENERGY STAR’s line is 15 years: past that, start pricing a replacement. Age alone doesn’t end a furnace, though. A cracked heat exchanger, a repair that’s a big share of a new furnace, or a repair every winter does.
Is it worth repairing a 20-year-old furnace?
For a flame sensor or an igniter, often yes. For a control board, a blower motor or anything to do with the heat exchanger, usually not. Lennox’s rule is to replace when a repair costs more than half of a new furnace, and Carrier says replacing a 20-year-old furnace is often the smart financial move.
How long does a Trane furnace last?
Trane says the average furnace lasts 15 to 20 years and a well-maintained Trane can last 20 or more. Its heat exchanger warranty runs from 20 years to the life of the furnace, depending on the model. We’re a Trane Comfort Specialist.
How long does a Carrier furnace last?
Carrier says most furnaces last 15 to 20 years and a high-quality one can potentially reach 30. We’re Carrier experts, and we install and service them.
How long does a Lennox furnace last?
Lennox puts it at 15 to 20 years and says one with annual maintenance should easily last over 15. We service Lennox furnaces along with every other major brand.
What are the signs a furnace is going out?
It’s past 15, the repairs keep coming, the gas bill climbs for no reason, rooms won’t warm up, new banging or grinding, cold air from the vents, or short cycles, rust, soot or a burning smell around it. Two or three of those on an older furnace is the time to get a replacement price.
Can a cracked heat exchanger leak carbon monoxide?
Yes. Lennox says a crack can let carbon monoxide into the home. Keep CO alarms on every level and outside the bedrooms, as CPSC advises, and if you suspect CO poisoning, get outside and call 911. What to do if your CO alarm goes off.
How long does it take to install a furnace?
Most replacements take one working day, with the heat back by evening. Switching from an 80% to a 95%, new ductwork or a tight space can stretch it, and a good estimate says so up front.
Does a yearly furnace tune-up really make it last longer?
Trane and Lennox both say so, and CPSC says to have the heating system inspected and serviced every year. Our heating check is $67 per system through December 31. Everything we’re running now.
What does a new furnace cost?
From us, $4,285 to $14,040 installed for a gas furnace, by size and efficiency. From about $71 a month at 0% APR for 60 months, the whole price financed, on approved credit. Washington Gas pays $500 or $700 back on qualifying ENERGY STAR furnaces rated 95.1% and up.
Should I replace my furnace and air conditioner at the same time?
If they’re about the same age, usually. Trane’s advice is to consider replacing the AC along with an old furnace, and it’s one install day instead of two. Both together run $8,898 to $23,000 installed. From about $148 a month at 0% APR for 60 months, the whole price financed, on approved credit.
Furnace past 15? Get a straight answer before the cold
If your furnace is in the 15-to-20 window, the useful move this month is a check, not a guess. You’ll know whether it has winters left, what’s wearing on it, and what a replacement would cost if it doesn’t, before the first cold snap decides for you.
Call (703) 997-9757, any hour, or book online. Holding someone else’s replacement quote? We’ll give you a free second opinion on it. Everything we do for heating is on our heating page.
More straight answers from our crew: how long a water heater lasts, how long an AC unit lasts, heat pump vs. air conditioner and what size AC unit you need.
SwiftPro Heating, Cooling & Plumbing repairs and replaces gas and propane furnaces across Northern Virginia, out of Chantilly and Ashburn. We’re a Trane Comfort Specialist, Carrier experts and a Rheem Pro Partner, and in Washington Gas’s contractor network for furnaces. Family owned, with 24/7 emergency service, Virginia Class A contractor license 2705192276, and rated 5.0 stars across 1,131 reviews on Google, Angi, Yelp, the BBB and Facebook. Read the reviews.
