Furnace Replacement Cost Calculator: 2027 Prices & BTU Size

How to Use the Furnace Calculator

The main fields cover most jobs. “Show More Options” adds ceiling height, insulation, air tightness, windows and sun exposure, which matter if your house is unusually tight, leaky, sunny or tall-ceilinged.

1. Home size. Heated square footage only. Leave out the garage and the crawlspace.
2. Furnace efficiency. 95% AFUE is the default because it’s what most people install now. If you can’t run new PVC vent pipe, switch to 80%.
3. Fuel type. Gas or oil. Pick oil and efficiency switches to 85% AFUE, since that’s what oil furnaces come in. Propane units cost about the same to install as gas, so price propane with the gas setting.
4. Project type. Swapping out a working system is “Replace Old System.” New construction and gut renovations usually need ducts too, and picking new construction switches the duct field for you.
5. Air ducts. “Need to Install Ducts” adds new insulated duct (R-8) to the price and asks how many floors the house has.
6. Climate region. It’s filled in from your location. Check it against the zone map under the calculator, because colder regions need more BTUs per square foot.

Hit Calculate and you get the heat load, the recommended furnace size and three installed prices: low end, mid range and high end. Most people pay near the middle figure. An experienced tech who just opened his own shop will often quote near the low end and still do great work.

What a New Gas Furnace Costs

For a 2,000 sq. ft. house with average insulation, a 100,000 BTU, 95% AFUE gas furnace runs $7,480 to $9,230 installed at typical rates, and most homeowners land near $8,400. Northeast and West Coast labor can push the top end toward $9,910 to $10,900.

That covers the unit, venting, labor and the contractor’s margin. New or upsized ductwork is priced separately.

Where the money goes

• Equipment: about $3,560 to $4,410. Furnace, vent pipe, drain fittings and small parts.
• Labor: about $3,310 to $4,070. Setting the unit, venting, hookups and startup.
• Tear-out and setup: about $600 to $770. Pulling and hauling away the old furnace.

Overhead and profit are already in those numbers: trucks, office, warranty callbacks. Don’t begrudge it. A contractor who isn’t making money won’t be around when your igniter fails in year three.

Adding a heat pump for a “dual fuel” setup stacks its cost on top of the furnace, so the total usually starts around $13,360. The heat pump cost calculator prices that half of the job.

Gas, Oil or Propane: What It Costs to Run

The install is a one-time bill. Fuel comes due every winter. Here’s roughly what a 1,900 sq. ft. Massachusetts home burns in a season (95% gas or propane furnace, 85% oil furnace):

Fuel	Fuel used per season	Typical cost vs. gas
Natural gas	About 1,160 therms	Baseline
Heating oil	About 930 gallons	Often a third more
Propane	About 1,270 gallons	Often double or more

Fuel prices move by month and by state. For dollar figures where you live, run your system through the home heating cost calculator.

80% vs. 95% AFUE: Is High Efficiency Worth It?

AFUE is the share of fuel that ends up as heat in your house. An 80% furnace sends a fifth of every fuel dollar up the flue, while a condensing 95-97% unit loses only 3-5%. Replacing a tired 76% furnace with a 95-97% model can cut fuel use by roughly 20%.

Check two things before you sign:

• Rebates. Many utilities and state energy programs pay cash back on 95%+ AFUE furnaces with variable-speed (ECM) blowers. Amounts vary a lot by state and utility, so look them up before you pick a model. Good installers handle the paperwork.
• Your ducts. ECM blowers move more air. Undersized ducts choke them, and the efficiency you paid for quietly disappears. Ask the installer to measure static pressure.

Fix the Leaks Before You Buy Extra BTUs

A 98% furnace won’t save much if the heat escapes before it reaches the rooms. In most older homes the bigger losses are elsewhere:

• Uninsulated ducts can waste 25-30% of your heat, especially runs through an attic or crawlspace. On a $400 winter heating bill, that’s $100 or more a month warming dead space. Price the fix with the ductwork cost calculator.
• The attic comes next. Bringing it up to spec can cut total heat loss 10-15%. See the attic insulation cost calculator.
• Empty wall cavities filled with blown-in or spray foam insulation can knock off another 7-10%.
• Triple-pane windows help too, but only about 5-7%, which makes them the slowest payback of the four.

Tighten the house first and you may drop a furnace size, which saves money on the install and every winter after.

How the Calculator Sizes Your Furnace

It starts with BTUs per square foot for your climate region, then adds two losses that quick sizing charts skip:

• Duct loss: a flat 8.5%. Leaky, uninsulated runs can lose 15% or more.
• Venting loss: about 20% for an 80% unit versus 3-5% for a condensing model, which is why an 80% furnace often comes out a size bigger.

Residential furnaces top out around 125,000 BTU, so homes over about 3,000 sq. ft. may need two. The calculator stacks 125K units and covers the remainder with a 40K, 60K, 80K, 100K, 110K or 120K unit. A 160K load gets priced as 125K plus 40K, though two 80K units would come in a little lower.

Treat the size as a starting point. The final equipment call belongs to you and your installer, ideally backed by a room-by-room HVAC load calculation. For a second opinion on size alone, the furnace size calculator runs the BTU math by itself. If you heat with hot water instead of air, use the boiler cost calculator.

Furnace Sizing and Venting Questions

What size furnace does a 2,000 sq. ft. house need?

With average insulation in a cold climate, about 100,000 to 110,000 BTU. Tighter houses and milder regions need less, so run your own numbers.

Can I vent a high-efficiency furnace into my old chimney?

No. Condensing furnaces make cool, wet exhaust that has to leave through sealed PVC pipe, usually out a side wall. If that isn’t practical, an 80% unit is the fallback.

When you compare quotes from local furnace installers, ask each one to write the model, BTU size and AFUE on the bid. If one price is far below the rest, check whether it includes the venting, the condensate drain and the permit.