Furnace Replacement Cost by Home Size and Sizing Mistakes
What a furnace replacement costs for a typical home, how oversizing inflates the quote, and what the installer's price should include.
A furnace replacement typically costs $6,000, with most mid-range jobs between $4,700 – $7,800 before sales tax. A basic swap starts around $4,550, and a premium install with ductwork changes reaches $9,600. Those figures are for our default 186 m² (about 2,000 sq ft) home, so use them as the middle of the range and adjust for your own house.
Our Furnace replacement covers the full breakdown. This article covers the part people get wrong: how house size changes the price, and why a bigger furnace is not a better one.
How home size changes the price
Size matters less than most people expect. The furnace is a single piece of equipment, and labor to remove the old unit and set the new one is similar in a small house and a large one. What changes with size is:
- Capacity. Bigger houses with more heat loss need a larger unit, which costs more.
- Staging. Large homes benefit more from two-stage or modulating furnaces, which sit in the upper tiers.
- Ductwork. More rooms mean more duct to seal, modify or partly replace.
- Access. A big house with the furnace in an attic or crawlspace costs more than the same job in a basement.
So a small house with a simple basement install lands toward the low end of the mid range. A large house with attic access and duct changes pushes toward the top. Square footage alone is a poor predictor, and any quote that is just a per-square-foot multiple should make you ask what it leaves out.
Equipment type matters as much as size
The type of furnace moves the price more than a few hundred square feet either way. Typical mid-range costs for our default home:
| Furnace type | Typical cost |
|---|---|
| Gas, 80% AFUE, single-stage | $4,900 |
| Gas, 95-96% AFUE, single-stage | $6,000 |
| Gas, 96% AFUE, two-stage, variable-speed blower | $7,300 |
| Gas, 97-98% AFUE, modulating | $9,000 |
| Electric furnace | $3,900 |
| Oil furnace, 85-87% AFUE | $7,000 |
For the full table with usual ranges and lifespans:
| Material | Typical | Usual range | Lifespan |
|---|---|---|---|
| Electric furnace | $3,900 | $3,050 – $5,050 | 20-30 years |
| Gas, 80% AFUE, single-stage | $4,900 | $3,800 – $6,350 | 15-20 years |
| Gas, 95-96% AFUE, single-stage | $6,000 | $4,700 – $7,800 | 15-20 years |
| Oil furnace, 85-87% AFUE | $7,000 | $5,450 – $9,100 | 15-20 years |
| Gas, 96% AFUE, two-stage, variable-speed blower | $7,300 | $5,700 – $9,500 | 15-20 years |
| Gas, 97-98% AFUE, modulating | $9,000 | $7,000 – $11,700 | 15-20 years |
The sizing mistake that raises your quote
The most common error is replacing the old furnace with the same size, or one size up "to be safe." Neither is a calculation. The old unit may have been oversized from the start, and the house has likely changed since: new windows, added insulation and air sealing all reduce heat loss.
An oversized furnace costs you in three ways:
- A higher purchase price. A larger unit with more capacity costs more, and the extra is wasted.
- Short cycling. The furnace heats the house quickly, shuts off, and repeats. That wears out components and leaves uneven temperatures between rooms.
- Comfort and noise. Short bursts of high airflow are louder and can feel drafty, and the system rarely runs long enough to even out the temperature.
An undersized unit is the opposite problem: it runs constantly and struggles on the coldest days. The fix for both is a proper load calculation (often called a Manual J) done for your house. Ask for it in writing. If a contractor sizes by looking at the old nameplate or by square footage, treat that as a warning sign.
Two quick checks. First, if you have replaced windows or added insulation since the old furnace went in, the right size is probably smaller than what is there now. Our Window replacement shows what that upgrade costs. Second, get at least two quotes with the calculated load stated. If the sizes differ widely, ask each contractor to explain the difference.
What the quote should include
A fair furnace quote lists these items separately, not as one lump sum:
- Removal and disposal of the old unit
- The furnace model, efficiency rating and stage type
- Venting: reusing the existing flue, or new PVC venting and condensate drain (required for most high-efficiency units)
- A chimney liner if a gas water heater still vents through the old flue
- Duct work: plenum and transition changes, sealing, or partial replacement
- Thermostat, gas line and electrical connections
- Permit and inspection. Plumbing, electrical and structural changes usually need a local permit, and your contractor should say who pulls it.
- Labor and parts warranty terms
The venting and duct lines are where quotes diverge. A high-efficiency furnace that needs new venting, plus duct changes, can cost far more than a like-for-like swap, so make sure you compare quotes with the same scope. Attic or crawlspace access also adds labor.
Related decisions
- Water heater. If your gas water heater shares the old chimney, switching to a high-efficiency furnace may mean a liner or a new water heater. See our Water heater replacement.
- Switching to a heat pump. If you are weighing electric heating, compare against the Heat pump installation, including the dual-fuel option that keeps a gas furnace as backup.
- Electrical capacity. Going electric can strain an older panel. Our House rewiring guide covers what a panel upgrade involves.
Rebates and tax
The federal 25C credit no longer applies to property placed in service after 31 Dec 2025. Some states run IRA home energy rebate programs, and utilities often offer rebates on efficient equipment. Availability varies by state, so check the DSIRE database for state and utility incentives before you sign. Sales tax on materials varies by state, and our figures are before tax.
How we calculate
We build furnace figures from labor hours times local rates plus equipment and materials, then check them against market prices and real quotes. We do not price by square footage alone, because equipment type, venting, ducts and access drive the total.
When quotes arrive, run them through our quote checker ("is my quote fair") to see whether each sits inside the expected range for your scope. A quote well above the range often traces back to an oversized unit or bundled extras. One well below it may be leaving out venting, permits or disposal.