Furnace replacement cost
Updated 2026-11-07 · By the HVAC Service Estimator team
Replacing a gas furnace typically costs about $3,800 to $10,000 installed, according to Angi's 2026 figures - and that range deliberately excludes ductwork, gas line work and a thermostat. For a concrete reference point inside that band, Trane's own pricing guide puts an 80% efficiency single-stage furnace at $5,093 to $5,481 installed. If the air conditioning is being replaced at the same time, you are buying a full system, which Angi averages at about $7,500.
What a furnace replacement costs
Two things are in every furnace quote: the appliance, which is a material cost, and the installation, which is labor plus the materials needed to connect it - venting, gas piping, sheet metal, electrical, condensate. The published ranges below describe the appliance plus a normal installation. They do not describe a house where the ducts have to be rebuilt.
| Scope | Typical installed cost | Source and notes |
|---|---|---|
| Gas furnace replacement, overall | $3,800-$10,000 | Angi 2026; excludes ductwork, gas line and thermostat |
| 80% efficiency, single-stage | $5,093-$5,481 | Trane published pricing guide (manufacturer) |
| Full system, furnace plus AC - average | About $7,500 | Angi 2026 national average |
| Full system, common band | $7,000-$15,000 | Where most 2026 quotes land |
| Full system, full published range | $5,000-$22,000 | Angi 2026 |
| Central AC side, if replaced with it | $3,900-$7,900 | 2026 cost guide, cooling side alone |
The Trane figure is useful precisely because it is narrow and comes from the manufacturer: it tells you what a basic, honest, mid-market 80% single-stage furnace installation actually costs when nothing unusual is going on. Angi's wider $3,800 to $10,000 range is the same job plus every variation - efficiency, staging, blower type, access, and local labor rates.
What drives the price
Efficiency and venting
An 80% furnace vents through metal flue pipe, often into an existing chimney liner or a B-vent. A condensing furnace in the 90s vents through PVC to the outside wall or roof, with a matching intake, and it produces acidic condensate that needs a drain and usually a neutralizer. Moving from 80% to condensing is not just a more expensive box - it changes the installation. If the old 80% furnace shared a chimney with a gas water heater, pulling the furnace off that chimney can leave the water heater orphaned and unable to vent properly, which is another real line item.
Staging and blower
Single-stage furnaces are on or off. Two-stage and modulating furnaces run at reduced capacity most of the time, which is quieter and more even. An ECM variable-speed blower costs more than a PSC blower and matters more than most homeowners expect, because it is also the blower your air conditioning depends on.
What has to be rebuilt around it
- Sheet metal plenum and the transition to the evaporator coil, if there is one
- Gas piping and a new sediment trap and shutoff
- Venting, and a chimney liner if the water heater is now orphaned
- Condensate drain and neutralizer on a condensing furnace
- Electrical: a dedicated circuit and a service switch
- Permit and inspection
Ductwork
Angi's exclusion is the important detail here. A furnace is only as good as the duct system it is attached to, and a new high-static furnace on an undersized duct system will not deliver its rated airflow. If a contractor measures static pressure and tells you the ducts are the problem, that is good news badly timed - see ductwork replacement cost for what drives that side of the job.
Sizing: confirm the Manual J
Furnaces in existing houses are oversized far more often than they are undersized, because the easy thing to do is match the old nameplate. The old unit was frequently sized by the same shortcut decades ago, and the house may have had windows, insulation or air sealing added since. An oversized furnace reaches setpoint fast, shuts off, and repeats - short-cycling that is hard on the heat exchanger and the igniter, and uncomfortable to live with.
Ask for the Manual J result in writing. A load calculation needs the house: orientation, window area and glazing, insulation levels, infiltration, duct location and duct losses. Nobody can do that from a photograph of the furnace.
Commissioning a gas furnace
On a gas appliance, startup is not optional and it is measurable. A competent installer will:
- Clock the gas meter or check manifold pressure to confirm the firing rate against the rating plate
- Run a combustion analysis - measure flue gas oxygen or carbon dioxide, carbon monoxide and stack temperature
- Measure the temperature rise across the heat exchanger and confirm it sits inside the range printed on the unit
- Measure total external static pressure to confirm the duct system can move the required air
- Verify draft and that the venting is correct and clear, and that no other appliance has been orphaned
- Hand you a startup sheet with those numbers on it
A furnace that fires but has not been combustion-tested is a furnace nobody has verified. Ask for the numbers.
Repair or replace?
A furnace with a cracked heat exchanger is done - that is a safety condemnation, not a judgment call. Short of that, the usual decision points are age, the cost of the specific failure, and whether the AC side is also near the end of its life. If both are old, doing them together saves a second trip charge, a second permit, and building the sheet metal transition twice, which is why the full-system average of about $7,500 overlaps so much with the sum of the individual jobs. See AC replacement cost for the cooling half, and heat pump cost if you are considering heating with electricity instead.
Getting a comparable quote
Ask each bidder for the model number, the efficiency and staging, the Manual J result, whether a permit is included, how the furnace will vent, whether the water heater's venting is affected, and which commissioning measurements they will document. With HVAC Service Estimator HVAC+ you can lay out the appliance, installation labor, venting, gas, electrical and permit as separate lines at local rates, so you can see at a glance which quote is missing something. An app estimate is a planning tool, not a bid.
Frequently asked questions
Does the $3,800-$10,000 range include ductwork?
No. Angi's 2026 furnace range specifically excludes ductwork, gas line work and the thermostat. On a straightforward swap into an existing, adequate duct system those exclusions do not matter much. On an older house where the ducts are undersized, leaky or in the wrong place, they can be the largest items on the quote - which is exactly why they are quoted separately.
What is the difference between an 80% and a 90-plus furnace?
The number is the annual fuel utilization efficiency: an 80% furnace sends about 20% of the fuel energy up the flue, a condensing furnace in the 90s recovers much of that by condensing water out of the exhaust. The condensing furnace costs more up front and burns less gas, but it also needs PVC intake and exhaust piping routed to the outside and a condensate drain with a neutralizer, so the installation is a bigger job. Trane publishes $5,093 to $5,481 for an 80% single-stage unit; a condensing, multi-stage or variable-speed furnace sits higher in the $3,800 to $10,000 band Angi describes.
Do I need a permit to replace a furnace?
In most jurisdictions, yes. A gas appliance changeout involves combustion, venting and gas piping, which is precisely the kind of work inspection exists for. Expect the permit as a real line item on the quote, and expect an inspection. A contractor offering to skip it is offering to leave unpermitted gas work in your house.
How do I know the new furnace is the right size?
A Manual J load calculation on your actual house - not a rule of thumb per square foot, and not the size of the old unit read off its nameplate or a photo. Oversized furnaces short-cycle, blow uncomfortably hot air in bursts, and wear out their heat exchangers and ignition components faster. Ask to see the load calculation result before you sign.
Sources
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