A furnace is sized in BTU of heat output, not in tons. That single difference is why a square-footage chart built for air conditioners will steer you wrong on a furnace, and why two identical 2,000 sq ft houses can need furnaces that differ by 60,000 BTU. Your climate zone, not just your floor plan, sets the number.
TL;DR: A replacement furnace runs $2,800–$11,000 installed in 2026 across home sizes from 1,000 to 3,000 sq ft. Sizing runs 30–60 BTU per square foot depending on climate zone, so a 2,000 sq ft home needs 60,000–70,000 BTU in a warm climate and 100,000–120,000 BTU in a cold one. The federal minimum is still 80% AFUE; the 95% AFUE rule applies to furnaces manufactured on or after December 18, 2028. Run your numbers in the estimator.
How Much Does a Furnace Cost by Home Size?
A replacement furnace costs $2,800 to $11,000 installed in 2026, and where you land depends on two things: the BTU output your square footage requires, and the efficiency tier you buy. A 1,000 sq ft home on a budget 80% AFUE single-stage furnace sits at the $2,800 floor. A 3,000 sq ft home on a premium modulating unit reaches the $11,000 ceiling. Every price in the table below falls inside that range.
Furnace Installed Cost by Home Size and Efficiency Tier (2026)
| Home Size | Budget (80% AFUE single-stage) | Mid-Range (96% AFUE two-stage) | Premium (97%+ modulating) |
|---|---|---|---|
| 1,000 sq ft | $2,800–$4,000 | $3,800–$5,500 | $5,500–$7,500 |
| 1,500 sq ft | $3,000–$4,300 | $4,200–$6,000 | $6,000–$8,000 |
| 2,000 sq ft | $3,300–$4,800 | $4,600–$6,800 | $6,800–$9,000 |
| 2,500 sq ft | $3,700–$5,400 | $5,200–$7,600 | $7,600–$10,000 |
| 3,000 sq ft | $4,200–$6,200 | $6,000–$8,800 | $8,500–$11,000 |
The step-up between brackets is smaller than most homeowners expect. Read down the mid-range column: the low end moves from $3,800 at 1,000 sq ft to $6,000 at 3,000 sq ft, which is $2,200 spread across 2,000 extra square feet, or $1.10 per sq ft. The high end moves from $5,500 to $8,800, which is $3,300 across the same 2,000 sq ft, or $1.65 per sq ft. In plain terms, each additional 1,000 sq ft adds roughly $1,100 to $1,650 at the mid-range tier. Jumping one efficiency tier costs more than adding 1,000 sq ft of house.
This page covers the furnace only. If you are replacing the air conditioner at the same time, the combined project is priced differently: see HVAC cost by home size for whole-system pricing in tons, or the AC and furnace replacement cost guide for bundled quotes.
How Many BTUs Does Your Furnace Need per Square Foot?
Between 30 and 60 BTU per square foot, and the spread is entirely climate. Warm southern climates (Zones 1 to 2) need 30 to 35 BTU per sq ft. Mixed climates (Zone 3) need 40 to 45. Cool climates (Zone 4) need 45 to 50. Cold northern climates (Zone 5 and above) need 50 to 60. Multiply your conditioned square footage by the band for your zone and you have the heat output your furnace has to deliver.
Furnace BTU Output Needed by Square Footage and Climate Zone
| Home Size | Zone 1–2 Warm (30–35 BTU/sq ft) | Zone 3 Mixed (40–45) | Zone 4 Cool (45–50) | Zone 5+ Cold (50–60) |
|---|---|---|---|---|
| 1,000 sq ft | 30,000–35,000 | 40,000–45,000 | 45,000–50,000 | 50,000–60,000 |
| 1,500 sq ft | 45,000–53,000 | 60,000–68,000 | 68,000–75,000 | 75,000–90,000 |
| 2,000 sq ft | 60,000–70,000 | 80,000–90,000 | 90,000–100,000 | 100,000–120,000 |
| 2,500 sq ft | 75,000–88,000 | 100,000–113,000 | 113,000–125,000 | 125,000–150,000 |
| 3,000 sq ft | 90,000–105,000 | 120,000–135,000 | 135,000–150,000 | 150,000–180,000 |
There is a ceiling hiding in that table. Standard residential gas furnaces top out around 120,000 BTU of input rating, so any cell above roughly 120,000 BTU of required output cannot be covered by one furnace. That is the 2,500 sq ft cold column and both the cool and cold columns at 3,000 sq ft. Those homes need two furnaces or a zoned system. That is a separate project priced outside the single-furnace ranges on this page, and it typically adds $2,000 to $5,000 on top of them.
These bands are a starting point, not a spec. A Manual J load calculation is the only method that accounts for your actual insulation, window area, ceiling height, and air leakage, and it routinely moves the answer by 10,000 to 20,000 BTU in either direction. Ask for the Manual J output before you sign anything.
What Size Furnace Does a 2,000 Sq Ft Home Need in Each Climate Zone?
A 2,000 sq ft home needs anywhere from 60,000 to 120,000 BTU of output depending on where it sits. That is a factor of two on the same floor plan, and it is the single biggest reason a national furnace sizing chart misleads people. Below is the same 2,000 sq ft house priced through all four zones at the mid-range tier, where most replacements land.
| Climate Zone | Example Metro | BTU Output Needed | Mid-Range Installed Cost |
|---|---|---|---|
| Zone 1–2 (warm) | Miami, Houston | 60,000–70,000 | $4,600–$5,300 |
| Zone 3 (mixed) | Atlanta, Charlotte | 80,000–90,000 | $5,000–$5,800 |
| Zone 4 (cool) | Kansas City, Philadelphia | 90,000–100,000 | $5,400–$6,200 |
| Zone 5+ (cold) | Chicago, Minneapolis | 100,000–120,000 | $5,900–$6,800 |
The Minneapolis homeowner pays about $1,300 to $1,500 more than the Miami homeowner for the same house, the same brand, and the same efficiency tier, purely because the heat exchanger and burner assembly are larger. Run that back through the table and the capacity premium works out to roughly $245 to $365 per additional 10,000 BTU of output: the mid-range column adds $2,200 at the low end and $3,300 at the high end across a 90,000 BTU capacity spread.
Working from a specific bracket instead? See HVAC cost for a 1,500 sq ft home or HVAC cost for a 3,000 sq ft home for whole-project pricing in those sizes.
Why Is the BTU on the Furnace Label Not the Heat You Get?
Because the nameplate number is fuel input, not heat delivered. An 80,000 BTU furnace burns 80,000 BTU of gas per hour; how much of that reaches your rooms depends on AFUE. At 80% AFUE, that unit delivers 64,000 BTU of usable heat and sends the other 16,000 up the flue. Homeowners who match the nameplate to their Manual J number end up undersized by a fifth, and it shows up as a furnace that cannot hold temperature on the coldest nights.
Nameplate Input Needed to Deliver 80,000 BTU of Output
| AFUE Rating | Nameplate Input Needed | Arithmetic |
|---|---|---|
| 80% | 100,000 BTU | 80,000 ÷ 0.80 |
| 90% | 88,900 BTU | 80,000 ÷ 0.90 |
| 96% | 83,300 BTU | 80,000 ÷ 0.96 |
| 98% | 81,600 BTU | 80,000 ÷ 0.98 |
There is a practical consequence for the 120,000 BTU ceiling mentioned earlier. At 80% AFUE, the largest common residential furnace delivers about 96,000 BTU of output. At 96% AFUE the same physical size delivers about 115,000 BTU. A high-efficiency furnace can therefore cover a home that a budget furnace cannot, which occasionally makes the condensing unit the cheaper answer once you price the alternative of two furnaces.
How Is Furnace Sizing Different From AC Tonnage?
They measure different loads and they are not interchangeable. A ton is a cooling unit equal to 12,000 BTU per hour of heat removal, and it is set by your summer cooling load. Furnace capacity is set by your winter heating load, which is a different calculation driven by outdoor design temperature rather than humidity and solar gain. The two numbers diverge most in cold climates, where the heating load can be double the cooling load on the same house.
- A 2,000 sq ft Minneapolis home might need only 2.5 tons of cooling but 100,000 to 120,000 BTU of heating. Small AC, large furnace.
- A 2,000 sq ft Houston home might need 4 tons of cooling but only 60,000 to 70,000 BTU of heating. Large AC, small furnace.
- The blower is shared. The furnace cabinet houses the blower that also moves your cooled air, so the furnace must be able to deliver the airflow the AC coil needs, which occasionally forces a slightly larger cabinet than heating alone would justify.
For the cooling side of the same question, our HVAC cost by home size page gives tonnage and whole-system pricing by square footage, and what size HVAC do I need walks through the tonnage chart by climate zone. This page is the heating counterpart to both.
What Do the 2026 Federal Furnace Efficiency Rules Actually Require?
As of August 2026, the federal minimum for a non-weatherized gas furnace is still 80% AFUE, the level set by a 2007 Department of Energy rule. You can still buy and install a non-condensing 80% furnace today, and roughly half the gas furnace market is still non-condensing. Nothing about the 2026 buying decision is restricted by a deadline this year.
The change on the horizon is real but further out than most sales pitches suggest. In September 2023 the DOE finalized a 95% AFUE minimum for non-weatherized and mobile home gas furnaces. Three details matter for a homeowner buying now:
- It applies to date of manufacture, not date of install. The standard covers furnaces manufactured on or after December 18, 2028. There is no contractor sell-through or installation deadline attached to it.
- It survived court challenge. A federal appeals court upheld the rule in a 2-1 decision on November 4, 2025, after gas industry groups argued it would eliminate non-condensing furnaces from the market.
- A delay has been requested but not granted. Gas industry groups petitioned DOE in February 2026 to move the compliance date to January 1, 2030 at the earliest. DOE published a notification of that petition on April 27, 2026 and took public comment through May 27, 2026. As of August 1, 2026 the December 2028 date still stands.
Practical read: if your furnace is failing now, buy the efficiency tier that pays back in your climate rather than the one a deadline is being used to sell you. A 96% AFUE furnace is worth the premium in Zones 4 and above, where the extra 16 points of efficiency work against a long heating season. In Zones 1 to 2 the payback often runs past the life of the equipment. The gas furnace replacement cost guide breaks the tiers down by brand. Note that the federal 25C energy efficiency home improvement credit is expired for 2026, so do not build it into your budget.
What Else Moves Your Furnace Price Beyond Square Footage?
Square footage sets the capacity. These five factors decide where inside your row of the cost table the quote lands, and the first three can appear as separate line items on top of it.
- Venting conversion ($600–$1,800). A condensing 96% AFUE furnace vents through PVC out a sidewall and cannot share the old masonry chimney. Switching from an 80% unit means new venting plus a condensate drain, and if a water heater was sharing that chimney it may need relining too.
- Fuel type. Electric furnaces skip the venting and gas line entirely and cost less to install, but usually more to run. Compare in the electric furnace replacement cost and gas vs electric furnace cost guides.
- Ductwork condition. A larger furnace pushes more air, and undersized or leaky returns will not carry it. Duct modification runs $500–$2,500 on a furnace-only job, well beyond that if the whole system is replaced.
- Ceiling height. The BTU-per-square-foot bands assume 8-foot ceilings. A room with 10-foot ceilings holds 25% more air to heat, which can push you a full size class up.
- Season and urgency. A January emergency replacement costs 10 to 15% more than the same job scheduled in spring or early fall, when contractors are quoting to fill the calendar.
Get a size-adjusted furnace estimate for your home →
Common Questions About Furnace Size and Cost
What size furnace do I need for a 2,000 sq ft home, and what does it cost?
A 2,000 sq ft home needs 60,000 to 70,000 BTU of heat output in a warm climate (Zones 1 to 2), 80,000 to 90,000 BTU in a mixed climate (Zone 3), 90,000 to 100,000 BTU in a cool climate (Zone 4), and 100,000 to 120,000 BTU in a cold climate (Zone 5 and above). Installed cost runs $3,300 to $4,800 for a budget 80% AFUE single-stage unit, $4,600 to $6,800 for a mid-range 96% AFUE two-stage, and $6,800 to $9,000 for a premium modulating furnace.
How many BTUs per square foot does a furnace need?
Between 30 and 60 BTU per square foot, depending on climate zone. Warm southern climates (Zones 1 to 2) need 30 to 35 BTU per sq ft. Mixed climates (Zone 3) need 40 to 45. Cool climates (Zone 4) need 45 to 50. Cold northern climates (Zone 5 and above) need 50 to 60. Multiply your conditioned square footage by the band for your zone to get required heat output, then have a Manual J load calculation confirm it against your actual insulation and windows.
How much does a furnace cost for a 1,500 sq ft house?
$3,000 to $8,000 installed in 2026. A budget 80% AFUE single-stage furnace runs $3,000 to $4,300, a mid-range 96% AFUE two-stage runs $4,200 to $6,000, and a premium modulating unit runs $6,000 to $8,000. On capacity, a 1,500 sq ft home needs 45,000 to 53,000 BTU of output in a warm climate and 75,000 to 90,000 BTU in a cold one.
Is furnace BTU the same as AC tonnage?
No. Tonnage measures cooling capacity, where 1 ton equals 12,000 BTU per hour of heat removal, and it is set by your summer cooling load. Furnaces are rated in BTU of heating output, set by your winter heating load. A home can need a 2.5 ton air conditioner and a 100,000 BTU furnace at the same time. Converting AC tonnage into furnace capacity is the most common furnace sizing mistake homeowners make.
Does a bigger furnace heat a house faster?
Briefly, then worse. An oversized furnace hits the thermostat setpoint quickly and shuts off, then restarts minutes later. That short-cycling wastes fuel, leaves cold spots in rooms farthest from the air handler, and shortens the life of the heat exchanger and blower. A correctly sized furnace runs longer, steadier cycles. Oversizing also costs money up front: at the mid-range tier, each additional 10,000 BTU of output adds roughly $245 to $365 to the installed price.
What is the minimum furnace efficiency required in 2026?
80% AFUE. That is the federal minimum for non-weatherized gas furnaces, set by a 2007 DOE rule and still in force as of August 2026. DOE finalized a 95% AFUE minimum in September 2023 that applies to furnaces manufactured on or after December 18, 2028, and a federal appeals court upheld it in November 2025. Gas industry groups petitioned DOE to move that date to January 1, 2030; the petition had not been granted as of August 1, 2026. The standard applies to date of manufacture, with no installation deadline.
What Should You Do With These Numbers?
Start with capacity, not price. Find your square footage row and your climate column in the BTU table, take that output figure to every contractor you call, and ask each of them to show the Manual J calculation that either confirms or corrects it. A quote that names a furnace model without naming a load calculation is a guess with a price attached.
Then pick the tier. In Zones 4 and above, the 96% AFUE mid-range column is usually the right answer on total cost of ownership. In Zones 1 to 2, where the furnace runs a few weeks a year, the budget column is defensible and the money is better spent on the cooling side. Either way, remember that the price you are comparing is a fully installed price: equipment-only quotes run 30 to 50% lower and are not comparable.
Related reading: Furnace Replacement Cost Guide · Gas Furnace Replacement Cost · Furnace Cost by Brand · HVAC Cost by Home Size · What Size HVAC Do I Need? · Best Time to Replace HVAC