Furnace Replacement Cost
Replacing a gas furnace costs $3,800–$12,000 installed depending on home size and AFUE efficiency — electric furnaces run just $1,700–$7,200. Price your fuel, size, and efficiency tier in seconds.
Three things set a furnace bill: the fuel — electric units install for a fraction of gas but cost more every winter after — your home's size, which fixes the BTUs, and for gas, the efficiency tier: how much of every therm becomes heat instead of going up the flue. That last one is a climate bet — the colder your winters, the faster high efficiency pays.
Gas or electric furnace?
Most homes replace like-for-like — check the old unit's label or whether a gas line feeds it. Electric costs far less to install but more to run in most markets; if you're considering the electric switch, compare a heat pump too.
How big is your home?
The heated square footage — it sets the furnace's size in BTUs at roughly 30–60 BTUs per square foot. Your installer confirms with a load calculation.
How efficient a furnace?
AFUE is the percentage of fuel that becomes heat. Standard (80–89%) is the entry point; moderate (90–95%) adds two-stage comfort and lower bills; 96%+ condensing furnaces cost the most and waste the least — worth most in cold climates with long heating seasons.
Cost to replace the furnace in a 1,800 sq ft home
$4,700–$8,000
unit and installation — ductwork modifications are a separate bill
Which AFUE tier actually pays for itself?
AFUE is the fraction of fuel that becomes heat — an 80% furnace sends a fifth of every gas bill up the flue; a 96% condensing furnace wrings out nearly all of it. The premium pays back through winters: in cold climates with big heating bills, the 96%+ tier earns its $3,700–$5,800 upcharge; in mild ones, the moderate 90–95% tier — often two-stage, noticeably more even heat — is the value pick. Also worth pricing while the old unit's out: our heat-pump comparison.
Right-sizing beats upsizing — insist on the load calculation
Furnaces size at roughly 30–60 BTUs per square foot, but the honest number comes from a load calculation of your insulation, windows, and climate. Oversizing isn't a safety margin — it costs more to buy, short-cycles, heats unevenly, and dies younger. A bid that names a BTU size without asking about your house is a guess; make every bidder show the math, and make them price ductwork issues as their own line.
Installed prices for a like-for-like replacement. Gas figures exclude ductwork modifications; electric figures exclude permits. Gas sizing runs 30–60 BTUs per square foot (40–50k BTUs for small homes up to 90–120k past 2,500 sq ft). AFUE tiers: standard 80–89%, moderate 90–95% (often two-stage), high 96%+ condensing. Electric units run $650–$5,600 before labor and are always 100% AFUE.
💡About this calculator▼
Furnaces die in winter — it's practically contractual — and the 2 a.m. replacement quote is the worst possible place to learn this market. Here's the pricing landscape in advance, organized by the three things that actually set the number: fuel, size, and efficiency.
Gas furnaces — the majority of American heating — run $3,800 to $12,000 installed. Size follows your square footage (roughly 30–60 BTUs per square foot: a small home takes a 40–50k BTU unit at $3,800–$6,700; past 2,500 sq ft you're at 90–120k BTUs and $5,800–$12,000). Efficiency is the real decision: AFUE measures how much of every therm becomes heat, and stepping from a standard 80–89% furnace to a 96%+ condensing unit adds $3,700–$5,800 up front while shrinking every heating bill after.
Electric furnaces are the quiet alternative with a sharp trade: $1,700–$7,200 installed — often a third of gas — no flue, no gas line, five extra years of lifespan, and every unit is 100% efficient by physics. The catch arrives monthly: resistance heat is the most expensive common way to warm a house in most markets, which is why anyone considering the electric switch should price a heat pump before a resistance furnace.
Pick your fuel, enter your square footage, and — for gas — choose your efficiency tier. And whatever the 2 a.m. contractor says, get the load calculation.
Fuel picks the table, size picks the row, and AFUE — for gas — adds its premium.
Gas. Published pricing runs by home size, because size fixes the BTUs: up to 1,200 sq ft takes a 40–50k BTU furnace at $3,800–$6,700 installed, 1,600–2,000 sq ft takes 60–70k BTUs at $4,700–$8,000, and 2,500+ sq ft takes 90–120k at $5,800–$12,000. On top of the size row rides the efficiency choice: standard 80–89% AFUE is the single-stage entry point; moderate 90–95% (often two-stage or variable-speed, noticeably more even heat) adds $1,400–$2,600; high-efficiency 96%+ condensing furnaces add $3,700–$5,800 and waste almost nothing.
Electric. Its own published table runs $1,700–$5,100 for smaller homes up to $2,300–$7,200 at 2,600–3,200 sq ft — and the efficiency question disappears, because every electric furnace converts 100% of its electricity to heat. What you save at install you repay at the meter: resistance heating costs more per delivered degree than gas in most markets, which this page says plainly rather than footnoting.
What neither table includes: ductwork modifications (gas source's own footnote) and permits (electric's). Both are the usual suspects when a real bid lands above these ranges.
📐How it's calculated▼
Gas: size-based band + efficiency premium.
Size rows (installed): up to 1,200 sq ft (40–50k BTUs) $3,800–$6,700 · 1,200–1,600 (50–60k) $4,200–$7,200 · 1,600–2,000 (60–70k) $4,700–$8,000 · 2,000–2,500 (70–90k) $5,100–$9,500 · 2,500+ (90–120k) $5,800–$12,000.
Efficiency premium over standard 80–89% AFUE: moderate 90–95% +$1,400–$2,600 · high 96%+ +$3,700–$5,800 — derived from the published efficiency tiers ($3,800–$6,200 standard, $5,200–$8,800 moderate, $7,500–$12,000 high, installed).
Electric: size-based band, no efficiency tier. 1,300–1,600 sq ft $1,700–$5,100 · 1,600–1,900 $1,800–$5,300 · 1,900–2,200 $2,000–$5,500 · 2,200–2,600 $2,200–$6,200 · 2,600–3,200 $2,300–$7,200. Every electric furnace is 100% AFUE.
Sizing behind the rows: 30–60 BTUs per square foot, refined by a load calculation in any real bid.
📎Sources:HomeGuide — Gas Furnace Prices (2026): installed costs by home size, BTU sizing, and AFUE efficiency tiers,HomeGuide — Electric Furnace Cost (2026): installed costs by home size, lifespans, and efficiency characteristics
🔍Finding your inputs▼
Gas or electric? Most replacements are like-for-like — check the dying unit's data plate, or simply whether a gas line feeds it. Switching directions is a bigger conversation: gas-to-electric should trigger a heat-pump comparison (resistance furnaces are the expensive way to electrify), and electric-to-gas hinges on whether a gas line exists or must be run.
How big is your home? Heated square footage — it maps to the furnace's BTU capacity at 30–60 BTUs per square foot. Treat the result as the bid-checking range: the installer's load calculation (insulation, windows, climate) makes the final sizing call, and it can shift a borderline home up or down a row.
How efficient a furnace? (Gas only.) The honest framework is your winter: in cold climates burning serious gas November through March, the 96%+ condensing tier's $3,700–$5,800 premium comes back through bills — and those units need a PVC flue and condensate drain, part of their higher install cost. In mild climates, the moderate 90–95% tier is the value pick, with two-stage comfort as the bonus. The 80s-AFUE standard tier is the right answer mainly for mild winters and tight budgets.
⚠️Special situations▼
My furnace died mid-winter — how do I avoid panic-buying?
Triage first: space heaters for the occupied rooms buy you 48 hours, and 48 hours is enough for two phone quotes. Emergency replacement is this market's worst pricing, and the classic upsell is a bigger, fancier unit 'while we're here.' A like-for-like replacement at your existing size and tier is almost always defensible under time pressure — the efficiency upgrade debate can happen on your schedule next time; surviving this week can't.
I'm choosing between repairing the old furnace and replacing it
Run the age math: furnaces live 15–25 years (electric 20–30), so a $900 repair on a 20-year-old gas furnace is buying months. The two signals that end the debate: a cracked heat exchanger (that's a replacement, full stop — it's the carbon monoxide boundary) and repair quotes hitting half the cost of new. Our HVAC repair-cost page prices the fix side of this decision.
Should I switch from gas to electric — or to a heat pump?
If the goal is leaving gas, the resistance furnace is usually the wrong vehicle: it installs cheap but heats expensive. A heat pump delivers 2–3 units of heat per unit of electricity (versus the furnace's 1:1), and in most climates it's the electric option that competes with gas on running cost — our heat-pump-vs-gas-furnace page runs that exact comparison with your numbers. The resistance furnace's honest niche: mild climates, small homes, and budgets where install price rules.
The bid wants to upsize the furnace "for safety margin"
Push back with the question that separates pros from guessers: where's the load calculation? Oversized furnaces cost more, short-cycle (blasting heat then shutting off), heat unevenly, and wear out early — the margin isn't safety, it's markup. Legitimate reasons to size up exist (an addition, degraded insulation, a converted attic), and they all show up in a Manual-J-style calculation. 'We always add 20%' does not.
My furnace shares ductwork with an aging AC — replace both?
If the AC is 12+ years old, price the combo: the labor overlaps, matched systems share a blower properly, and combo pricing routinely beats two separate installs a year apart. If the AC is young, just confirm the new furnace's blower is compatible with it. The same logic applies in reverse on our central-AC page — whichever half dies first, the other half's age belongs in the decision.
❓Common questions▼
How much does it cost to replace a furnace?
A gas furnace replacement costs $3,800–$12,000 installed, with home size and efficiency setting the number: small homes with standard-efficiency units sit near $3,800–$6,700, while large homes with 96%+ condensing furnaces reach $12,000. Electric furnaces run far less up front — $1,700–$7,200 installed — but cost more to operate in most markets. Figures exclude ductwork modifications.
What size furnace do I need?
Roughly 30–60 BTUs per square foot: homes up to 1,200 sq ft take 40–50k BTU furnaces, 1,600–2,000 sq ft homes take 60–70k, and homes past 2,500 sq ft take 90–120k. The refinement comes from a load calculation — insulation, windows, ceiling heights, climate — which any legitimate bid should include. Both directions of wrong sizing cost you: undersized runs constantly, oversized short-cycles and dies young.
Is a high-efficiency furnace worth the extra cost?
It's a climate bet with clean math: the 96%+ condensing tier adds $3,700–$5,800 over a standard furnace and reclaims roughly 10–16% of every gas bill (the fuel an 80s-AFUE unit sends up the flue). Cold-climate homes with $1,000+ heating winters recoup it well within the furnace's life; mild-climate homes often don't, making the moderate 90–95% tier — with its two-stage comfort — the value pick. One install note: condensing furnaces need PVC venting and a condensate drain, which is part of their premium.
How long does a furnace last?
Gas furnaces run 15–25 years; electric furnaces 20–30 — about five years longer, having no burners or heat exchanger to fatigue. The practical replacement signals beat the calendar: repair bills reaching half of replacement cost, uneven heating, short-cycling, rising gas bills, and — non-negotiably — a cracked heat exchanger, which ends the repair conversation on carbon monoxide grounds.
Why are electric furnaces so much cheaper to install but more expensive to run?
The install is simple — no gas line, no flue, no combustion safety work — so $1,700–$7,200 covers it against gas's $3,800–$12,000. But resistance heat converts electricity to warmth at exactly 1:1, and electricity costs more per unit of heat than gas in most markets, so winter bills run higher. That physics is also why heat pumps changed the conversation: they move heat rather than make it, delivering 2–3× the warmth per kilowatt-hour.
What should a furnace replacement quote include?
Five things itemized: the exact model and AFUE rating (not 'a high-efficiency unit'), the BTU size with the load calculation behind it, venting work (especially standard-to-condensing conversions, which need new PVC flues), any ductwork modifications as their own line, and the permit. Add the warranty split — parts (manufacturer) versus labor (installer) — and disposal of the old unit. Two bids with those pinned down are comparable; without them you're comparing adjectives.
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