How much does it cost to replace an HVAC system?

A straight AC-and-furnace replacement on existing ducts typically runs $9,000 to $19,000 installed for a mid-efficiency 3 to 4 ton system. A ducted heat pump is similar, a multi-zone mini-split runs $10,000 to $22,000, and replacing ductwork adds roughly $3.50 to $8.00 per square foot of house.

Is a bigger air conditioner better?

No — oversizing is the most common installation mistake. A too-large unit satisfies the thermostat in short cycles, never running long enough to pull humidity out of the air, so the house feels cold and clammy while the compressor wears faster. Correct sizing beats extra capacity, especially in humid climates.

What is a Manual J load calculation and do I need one?

It is a room-by-room calculation of heat gain and loss from your actual insulation, windows, orientation, air sealing and occupancy. It is the correct way to size equipment, and it is what separates a contractor doing the job from one copying the old nameplate. Yes, you should insist on one.

Is a higher SEER2 rating worth paying for?

It depends on your run hours. In a hot climate with long cooling seasons, moving from code minimum to a variable-speed system usually pays back through both energy and much better humidity control. In a mild climate with a short season, the roughly 50% equipment premium rarely returns in savings alone.

Do I have to replace the ductwork too?

Only if it is leaking, undersized for the new equipment, or contaminated. Test rather than assume — a duct leakage test costs a few hundred dollars and often shows sealing existing ducts delivers most of the benefit for a small fraction of replacement cost.

Heat pump or furnace and AC?

Modern cold-climate heat pumps hold usable capacity well below freezing and remove the combustion appliance entirely, which suits an all-electric house. Where gas is cheap and winters are severe, a dual-fuel setup — heat pump with a gas furnace as backup — is often the lowest operating cost.

HVAC Replacement Cost Calculator

Enter your home size or known tonnage, pick the system and efficiency tier, and get a low-to-high installed cost. The breakdown separates equipment from installation labor, ductwork, electrical and the permit and startup.

System type

Conditioned floor area(sq ft)

Used to size the system if you leave tonnage at 0. A rough screen only.

Known tonnage (0 to size from floor area)(tons)

Enter the tonnage from a Manual J load calculation if you have one.

Efficiency tier

Ductwork

Mini-split indoor heads(heads)

Only applies to a ductless system. Ignored for ducted systems.

Existing electrical adequate?

Regional market

Estimated total cost

$10,015 – $19,070

3.5 tons, ac + gas furnace

Most likely total: $14,543
System size usedScreened at 550 sq ft per ton — confirm with Manual J: 3.5tons
Equipment: $7,140 – $13,020
Installation labor: $2,625 – $5,250
Permit, startup & commissioning: $250 – $800

What this figure includes

These are installed prices for replacing residential equipment in an existing home: condenser or heat pump, indoor coil or air handler or furnace, line set connections, thermostat, refrigerant charge, permit, startup and commissioning, plus ductwork and electrical where selected. They exclude zoning systems, whole-house dehumidifiers, air cleaners and UV, gas line extensions, chimney relining, new returns beyond the existing layout, asbestos-wrapped duct removal, attic or crawlspace decking for access, and any structural work for a new equipment platform.

How this is calculated

The formula

Equipment replacement is priced per ton of cooling capacity, then adjusted:

Total = (tons × equipment rate + head cost) × efficiency factor + labor + ductwork + electrical + permit

Equipment rates differ by system. A condenser-and-coil AC replacement runs about $1,100 to $2,100 per ton in equipment. Add a gas furnace and it is $1,700 to $3,100. A ducted heat pump sits just below that, at $1,600 to $3,000, because it is one machine doing both jobs. A ductless mini-split is $1,300 to $2,400 per ton plus $600 to $1,400 for each indoor head, and heads are where a multi-zone job gets expensive.

Efficiency multiplies the equipment line only. Code-minimum single-stage is the baseline. A two-stage 16 to 17 SEER2 unit adds about 20%. A variable-speed inverter system at 18+ SEER2 adds about 50%.

Ductwork is priced separately, per square foot of conditioned area, at $3.50 to $8.00. On a 1,800 sq ft house that is $6,300 to $14,400 — frequently as much as the equipment. Which is why the honest answer to "should I replace the ducts?" is: only if they are leaking, undersized or full of something you would not want to breathe. A duct blaster test costs a few hundred dollars and answers it with a number.

Sizing: the mistake that matters most

Oversizing is the single most common and most damaging error in residential HVAC, and it is nearly always made in the direction of "bigger is safer".

A too-large air conditioner cools the thermostat's air to setpoint quickly and shuts off. That sounds good and is not. Cooling and dehumidifying are different jobs done by the same coil, and dehumidification takes time: the coil has to run long enough to get cold enough for moisture to condense on it and drain away. A short cycle satisfies the thermostat in eight minutes and never reaches that state. The result is a house at 72°F that feels clammy, with condensation on windows and a musty smell, plus more wear on the compressor from repeated starts and worse efficiency than the label promises.

In a humid climate this is not a comfort footnote — it is the entire question. A correctly sized 3-ton system that runs long cycles will make a Gulf Coast house feel far better than an oversized 4-ton that never runs.

Manual J, not square feet

This calculator screens capacity at roughly 550 square feet per ton so you have a starting figure. That rule of thumb is a screen, not a design. It knows nothing about your insulation, your window area and orientation, your air sealing, your ceiling height, your shading or how many people live there. Two identical 1,800 sq ft houses on the same street can honestly need 2.5 and 4 tons.

A Manual J load calculation is the actual method: room-by-room heat gain and loss from real inputs. A contractor who performs one — and will show you the output — is doing the job. A contractor who reads the tonnage off the old unit's nameplate is copying someone else's guess, including the guess that made the old unit oversized in the first place. Ask for Manual J, and for Manual S (equipment selection) and Manual D (duct sizing) if ducts are being touched. It is normal for a good contractor to charge for this.

A worked example

An 1,800 sq ft home, AC plus gas furnace, two-stage 16 SEER2, keeping existing ducts, adequate electrical, national pricing:

Tonnage screen: 1,800 ÷ 550 = 3.5 tons
Equipment: 3.5 × $1,700 to $3,100 × 1.2 = $7,140 – $13,020
Labor: 3.5 × $750 to $1,500 = $2,625 – $5,250
Permit, startup and commissioning: $250 – $800
Total: roughly $10,000 to $19,100

Replace the ducts as well and add $6,300 to $14,400 — the job nearly doubles.

Commissioning is not a formality

The last line item is the one that decides whether you got what you paid for. Refrigerant charge weighed in to the manufacturer's spec, airflow measured and set, static pressure checked, and the results written down. A high-efficiency system installed on undersized ductwork at the wrong charge will underperform a cheap unit installed properly. Ask for the startup sheet.

Cost figures last reviewed 9 Sept 2026 · Residential HVAC equipment and installation pricing per ton of cooling capacity, by system type.

Frequently asked questions

How much does it cost to replace an HVAC system?: A straight AC-and-furnace replacement on existing ducts typically runs $9,000 to $19,000 installed for a mid-efficiency 3 to 4 ton system. A ducted heat pump is similar, a multi-zone mini-split runs $10,000 to $22,000, and replacing ductwork adds roughly $3.50 to $8.00 per square foot of house.
Is a bigger air conditioner better?: No — oversizing is the most common installation mistake. A too-large unit satisfies the thermostat in short cycles, never running long enough to pull humidity out of the air, so the house feels cold and clammy while the compressor wears faster. Correct sizing beats extra capacity, especially in humid climates.
What is a Manual J load calculation and do I need one?: It is a room-by-room calculation of heat gain and loss from your actual insulation, windows, orientation, air sealing and occupancy. It is the correct way to size equipment, and it is what separates a contractor doing the job from one copying the old nameplate. Yes, you should insist on one.
Is a higher SEER2 rating worth paying for?: It depends on your run hours. In a hot climate with long cooling seasons, moving from code minimum to a variable-speed system usually pays back through both energy and much better humidity control. In a mild climate with a short season, the roughly 50% equipment premium rarely returns in savings alone.
Do I have to replace the ductwork too?: Only if it is leaking, undersized for the new equipment, or contaminated. Test rather than assume — a duct leakage test costs a few hundred dollars and often shows sealing existing ducts delivers most of the benefit for a small fraction of replacement cost.
Heat pump or furnace and AC?: Modern cold-climate heat pumps hold usable capacity well below freezing and remove the combustion appliance entirely, which suits an all-electric house. Where gas is cheap and winters are severe, a dual-fuel setup — heat pump with a gas furnace as backup — is often the lowest operating cost.