Furnace Replacement Cost Calculator
| Furnace tier (80,000 BTU) | Mid installed | Honest band |
|---|---|---|
| 80% single-stage | $2,800 | $1,800 - $3,800 |
| 95% two-stage | $4,200 | $2,700 - $5,700 |
| 97% modulating | $5,500 | $3,600 - $7,400 |
| Size (95% two-stage) | Mid installed | Honest band |
|---|---|---|
| 60,000 BTU | $3,600 | $2,300 - $4,800 |
| 80,000 BTU | $4,200 | $2,700 - $5,700 |
| 100,000 BTU | $4,600 | $3,000 - $6,200 |
| 120,000 BTU | $5,000 | $3,300 - $6,800 |
A furnace replacement is priced by size and efficiency tier, and the honest spread is wide because the box is the cheap half: an 80,000 BTU gas furnace - the most common size in US homes - lands mid-band around $2,800 installed as an 80% single-stage, $4,200 as a 95% two-stage, and $5,500 as a 97% modulating unit, before the $400 haul-away and the venting surprises that live in the upper band.
The efficiency math is climate-dependent and it has a deadline: 95% AFUE saves roughly 15-17% of the gas an 80% unit burns, which pays back its premium in a few cold-climate winters and maybe never in a mild one. But federal law already moved - furnaces manufactured on or after December 18, 2028 must hit 95% AFUE - so the low tier is a purchase with an expiration date, not a permanent option.
What separates a clean quote from a mess: sizing (a Manual J load calc, not copying the old nameplate), venting (90%+ condensing units breathe through PVC, not your old chimney), and scope (line sets, drains, permits, haul-away). This calculator prices the swap; the band is where those three variables live.
How to use
- Pick the size closest to your current furnace input (the nameplate BTU label) - resist upsizing: oversizing short-cycles, wastes fuel and wears the ignitor.
- Pick the efficiency tier - if you burn gas six months a year, the 95% premium usually pays; if you are selling within five years, the 80% tier still clears federal law until the 2028 changeover.
- Include haul-away if you are not keeping the old unit - it is a $400 line that always exists in real quotes.
- Compare the mid and band against two or three bids, then make each bidder state sizing method, venting plan and permit line separately.
Frequently asked questions
How much does it cost to replace a gas furnace?
The common 80,000 BTU size lands mid-band at $2,800 installed as an 80% single-stage, $4,200 as a 95% two-stage, $5,500 as a 97% modulating, with honest bands running roughly two-thirds to one-and-a-third times those mids. Add $400 haul-away, a few hundred in permit costs, and attic or crawlspace premiums of 10-20% where access is hard.
Is a 95% AFUE furnace worth the extra cost over 80%?
In a cold climate, yes: the 95% unit burns roughly 15-17% less gas, which on a $1,200 winter gas bill saves about $200 a season - the typical $1,400 premium pays back in seven or eight winters and the unit lasts fifteen to twenty. In a mild climate the math may never close, which is exactly why the tier was optional - until the 2028 federal floor makes 95% the only new manufactured option anyway.
What size furnace do I need for my house?
The honest answer is a Manual J load calculation, not a rule of thumb: real needs run roughly 30-60 BTU per square foot depending on climate and insulation, so an 80,000 BTU furnace typically serves a well-sealed 2,000+ sq ft home or a draftier 1,500. Copying the old furnace nameplate fails because the old unit may have been wrong from day one - and oversizing is the expensive mistake: it short-cycles, hums, and wears parts.
Will a new high-efficiency furnace need new venting?
Usually yes, and it is the classic mid-job change order: 90%+ condensing furnaces vent through PVC pipe out a side wall and need a condensate drain, while an 80% unit can reuse the chimney with a liner check. Quote the venting before the crew arrives - retrofitting PVC through finished walls mid-install is where bands go bad.
Why does installation labor cost as much as the furnace?
Because the box is the easy part: a proper swap includes gas line connection and leak test, flue or PVC venting, condensate drain, electrical, thermostat wiring, startup combustion tuning, permit and inspection - half a day to a full day for a two-person crew. The $1,500-2,000 labor line is not padding; it is the difference between a furnace that runs and one that runs right.