Furnace Cost Calculator
A furnace quote bundles three different purchases: the box, the efficiency rating, and the labor to make it fit your house. Comparing quotes on the total alone hides whether you are paying for better equipment or just a busier contractor.
This calculator sizes the furnace from your home’s square footage, then prices it by fuel type, AFUE efficiency, and ductwork needs. If you are sizing the whole system rather than pricing the box, our AC tonnage calculator covers cooling, and the spray foam insulation cost calculator shows what tightening the envelope does to the load.
Quick Answer
A 2,000 sq ft home needs about 90,000 BTU/h. A natural gas furnace at 95% AFUE reusing existing ductwork: $4,500 x 1.3 = $5,850 mid estimate, ranging $4,972.50 to $7,020.
💡 Key takeaways
- Gas furnaces run $2,500-$7,500 installed; 95% AFUE models run $4,500-$8,000.
- AFUE multiplies the base price: 80% = 1.0x, 90% = 1.15x, 95% = 1.3x, 96%+ = 1.4x.
- Ductwork is the biggest surprise line: modifications add ~$1,500, new ducts ~$4,000.
- Replace when the repair exceeds half the replacement cost on a 15+ year old unit.
How furnace pricing works
A furnace quote has three independent parts: the box (sized in BTU/h), the efficiency rating (AFUE), and the installation reality (ductwork, venting, permits). The calculator prices each one.
Installed cost = fuel base price x AFUE multiplier + ductwork
A 2,000 sq ft home needs about 90,000 BTU/h. A natural gas furnace at 95% AFUE with existing ductwork: $4,500 x 1.3 = $5,850 mid estimate, ranging $4,972.50 to $7,020. The 45 BTU per sq ft sizing rule is a planning shortcut for heating climates; a Manual J load calculation is the professional method and the one to insist on before signing.
Furnace cost by fuel and efficiency
Fuel type sets the base price; AFUE multiplies it. These are 2026 installed ranges for typical replacements.
| Setup | Installed range | Notes |
|---|---|---|
| Gas, 80% AFUE | $2,500-$4,500 Budget | Cheapest box; vents through a chimney or B-vent |
| Gas, 95% AFUE | $4,500-$8,000 Most popular | Needs PVC venting and a condensate drain |
| Electric | $2,000-$4,500 | Cheap to install, expensive to run in cold climates |
| Oil | $4,000-$7,500 | Needs a tank and chimney; common in the Northeast |
| With ductwork changes | $5,000-$10,000 | New or modified ducts are the biggest cost adder |
Brand tier matters less than the AFUE number and the installer: premium brands (Carrier, Trane, Lennox) run $8,000 to $15,000 installed with longer warranties, while value brands (Goodman, Amana) land $3,500 to $7,000. The AHRI directory certifies the efficiency ratings all brands publish, so compare AFUE numbers rather than marketing claims.
Repair or replace?
The industry rule of thumb: if the repair costs more than half the replacement and the furnace is past 15 years, replace it. Four signs the end is near: rising fuel bills with no rate change, frequent repairs two winters running, uneven heat between rooms, and a cracked heat exchanger (a safety issue: carbon monoxide). A furnace lasts 15 to 20 years with annual maintenance; a $150 to $300 yearly tune-up is the cheapest life extension available. A leaky attic drives heating load more than most owners expect; our attic volume calculator helps quantify that part of the problem.
What competing calculators miss
The best furnace tools start from a national cost model and adjust for fuel, efficiency, size, and ductwork, which is the right architecture. Brand-by-brand pricing guides add useful context on warranty tiers. But most simple calculators price one flat number per fuel type with no AFUE math, and ductwork, the most common four-figure surprise, is missing from nearly all of them. None link the sizing step to the pricing step: they ask for your home size and then ignore it. This calculator does both jobs in sequence: size the box from square footage first, then price it by fuel, AFUE multiplier, and ductwork, with the planning range shown instead of a false-precision single number.
The annual tune-up: what it covers and why it pays
A professional tune-up runs $150 to $300 a year, and most manufacturer warranties require annual professional service to stay valid. Neglected furnaces lose 2 to 5 percent efficiency and die younger; maintained ones hit their rated lifespan. Here is what the visit should include.
| Task | Who | Cadence |
|---|---|---|
| Filter replacement | DIY | Monthly in heating season |
| Burner cleaning and adjustment | Pro | Annual |
| Heat exchanger inspection | Pro | Annual |
| Blower motor and belts | Pro | Annual |
| Thermostat calibration | DIY / pro | Annual |
| Venting and flue check | Pro | Annual |
The homeowner jobs are filters, keeping supply and return vents unblocked, and testing carbon monoxide detectors. Everything involving combustion stays with a licensed tech. And one finding ends the repair-versus-replace debate instantly: a cracked heat exchanger is a carbon monoxide risk and a safety replacement, not a repair decision.
Ductwork: the other half of the system
The best furnace on the market cannot heat a house through bad ducts. Typical duct systems leak 20 to 30 percent of their heated air into attics, crawl spaces, and wall cavities, which means a 95% AFUE furnace can deliver like an 80% one. If some rooms never get warm, the house is dusty no matter what you do, or bills stayed high after a furnace replacement, the ducts are the prime suspect.
You have two fixes. Sealing with mastic (not duct tape, which fails) at every joint typically costs $1,000 to $2,500 and is the best dollar-per-BTU upgrade in an older home. Full duct replacement runs $4,000 or more and makes sense when ducts are undersized, crushed, or routed through a scorching attic. Duct sizing follows its own standard (Manual D), and oversized or undersized runs create the hot-and-cold-room pattern no thermostat can fix.
Frequently asked questions
A gas furnace costs $2,500 to $7,500 installed, with most homeowners landing between $3,000 and $6,000 for a mid-range unit. High-efficiency models (95% AFUE and up) run $4,500 to $8,000; oil furnaces run $4,000 to $7,500; electric runs $2,000 to $4,500. New or modified ductwork can push any of these $1,500 to $4,000 higher.
In cold climates, 95% AFUE or higher usually pays back through fuel savings. In mild climates with short heating seasons, an 80% unit can be the rational choice. The ENERGY STAR program certifies high-efficiency models worth comparing.
A planning rule is 45 BTU/h per square foot of living space in heating climates: 90,000 BTU/h for 2,000 sq ft. The accurate answer comes from a Manual J load calculation that accounts for insulation, windows, and air leakage.
Replace when the repair exceeds half the replacement cost and the unit is past 15 years, when repairs recur winter after winter, or when the heat exchanger is cracked. Otherwise, repair and keep up annual maintenance.
Fifteen to 20 years with annual maintenance. Neglected units die younger; well-maintained ones with replaced wear parts can push past 20.
Natural gas is usually far cheaper per BTU of heat delivered than electric resistance heat, especially in cold climates. Electric furnaces cost less to install but much more to run; heat pumps change this math entirely.
A straightforward replacement takes about one day. New ductwork, venting changes, or electrical upgrades add days.
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References
- AHRI. “How and Why Certified.” How and Why Certified Accessed October 25, 2026.
- ENERGY STAR. “Heating and Cooling Guidance for Homeowners.” Heating and Cooling Guidance for Homeowners Accessed October 18, 2026.
- InterNACHI. “Inspecting Furnaces.” Inspecting Furnaces Accessed October 25, 2026.
- U.S. Department of Energy. “Purchasing Energy-Efficient Residential Furnaces.” Purchasing Energy-Efficient Residential Furnaces Accessed October 25, 2026.
- ASHRAE. “Standards and Guidelines.” Standards and Guidelines Accessed October 25, 2026.
- ACCA. “Bigger Frequently Not Better.” Bigger Frequently Not Better Accessed October 25, 2026.