The short answer
A heating and cooling replacement is one of the largest predictable expenses of owning a home. It is predictable because the equipment has a known life, usually 12 to 20 years, and the date it was made is printed on the unit. It is large because the price covers far more than the box: removal of the old equipment, refrigerant handling, new line sets or venting, electrical connections, a permit, and a day or two of skilled labor.
For a typical 2,000 square foot home with a 3-ton system and usable ductwork, expect about $5,400 to $9,400 for a central air conditioner alone, $4,800 to $8,600 for a gas furnace alone, $9,200 to $16,200 for both, and $6,500 to $11,300 for a ducted heat pump that replaces both. The calculator above adjusts those figures for your home.
How the calculator works
The estimate is built in four steps, and every assumption is shown on this page so you can check it.
- Capacity. If you do not choose a size, the calculator estimates cooling tons from your floor area and climate: one ton per 500 square feet in hot climates, 600 in mixed climates, and 700 in cold ones, rounded to the nearest half ton and limited to the residential range of 1.5 to 5 tons.
- Equipment and installation. Each system type has a fixed cost plus a cost per ton, with low, typical, and high values. Ductless systems are priced per indoor zone instead of per ton.
- Efficiency and scope. A mid-range system adds 15% to the equipment and installation line, and a high-efficiency system adds 35%. Duct repair, duct replacement, electrical work, a thermostat, and a permit are added as separate lines.
- Local cost level. Labor-driven lines are multiplied by 0.9 for lower-cost areas and 1.2 for high-cost metros.
The formula is: estimate = (fixed cost + cost per ton × tons) × efficiency factor × local factor + scope items. The replacement fund figure divides the typical estimate by the months your current system has left, based on its age and a typical service life.
Cost assumptions by system type
These are the standard-efficiency, national-baseline figures behind the calculator for a 3-ton system, before ductwork or electrical changes. They are planning ranges drawn from published 2026 contractor and manufacturer pricing guides, not quotes.
| System | Low | Typical | High |
|---|---|---|---|
| Central air conditioner only | $5,400 | $7,100 | $9,400 |
| Gas furnace only | $4,800 | $6,200 | $8,600 |
| Air conditioner + gas furnace | $9,200 | $12,000 | $16,200 |
| Ducted heat pump | $6,500 | $8,600 | $11,300 |
| Ductless mini-split, per zone | $3,000 | $4,500 | $6,500 |
The combined air conditioner and furnace price is about 10% less than the two jobs priced separately, because the crew, the permit, and the trip are shared.
What drives the price of a quote
Two homes of the same size can receive quotes thousands of dollars apart. These are the usual reasons.
- Capacity. Each additional half ton adds roughly $700 to $1,300. An oversized system costs more to buy and performs worse, so bigger is not safer.
- Efficiency tier. Single-stage equipment that meets the federal minimum is the least expensive. Two-stage and variable-speed systems cost more up front, run longer at lower output, and hold temperature and humidity more evenly.
- Ductwork. Reusing sound ducts costs nothing. Sealing and repairing leaky ducts typically adds $1,000 to $3,500. Replacing the duct system in a 2,000 square foot home commonly adds $3,000 to $9,000.
- Electrical work. Switching from a gas furnace to a heat pump, or adding air conditioning where there was none, may need a new circuit or more panel capacity. Budget $500 to $3,000.
- Access. Equipment in a tight attic or crawlspace takes longer to remove and install than a unit in an open basement or garage.
- Venting. A condensing furnace cannot use the old metal flue. It needs a new plastic vent to an outside wall and a condensate drain.
- Season and urgency. A system that dies in a heat wave is replaced on the contractor's schedule and price. Planned replacements in spring or fall give you time to compare bids.
Sizing: why the rule of thumb is only a start
Cooling capacity is sold in tons. One ton removes 12,000 BTU of heat per hour, and residential systems run from 1.5 to 5 tons. Furnaces are sized separately, by BTU of heat output. The square-feet-per-ton shortcut in this calculator is good enough for a budget, but it should never be the basis for the equipment you actually buy.
The industry method is a Manual J load calculation, published by the Air Conditioning Contractors of America. It uses your insulation levels, window area and orientation, ceiling height, air leakage, and local design temperatures. A well-insulated house can need a full ton less than the rule of thumb suggests. If you have added insulation or replaced windows since the current unit was installed, copying the old size will probably oversize the new one. An oversized system short-cycles, which wears parts faster, leaves the air clammy, and wastes energy. Ask every bidder whether the quote includes a load calculation.
Efficiency ratings in plain terms
- SEER2 measures cooling efficiency over a season. Higher is better. Since 2023, new central air conditioners must be at least 13.4 SEER2 in northern states and 14.3 SEER2 in southern states for most residential sizes.
- HSPF2 measures heat pump heating efficiency. The federal minimum for split-system heat pumps is 7.5 HSPF2, along with 14.3 SEER2 for cooling.
- AFUE is the share of a furnace's fuel that becomes heat in the house. The current federal minimum for gas furnaces is 80%. Condensing furnaces reach 95% or more.
Whether a higher tier pays for itself depends on how many hours the system runs. In a hot or very cold climate with high energy prices, the upgrade can pay back within the life of the equipment. In a mild climate it often does not, and the better reasons to upgrade are comfort and noise. Our guide to energy efficiency upgrades and their return walks through the payback math.
Refrigerant changes and older systems
The refrigerant in your current system affects the repair-or-replace decision. Systems installed before about 2010 generally use R-22, which has not been produced or imported in the United States since 2020, so a leak repair relies on a shrinking supply of reclaimed refrigerant. Systems from roughly 2010 through 2024 use R-410A. New residential equipment made since 2025 uses lower-impact refrigerants, mainly R-454B and R-32. The refrigerants are not interchangeable, so a major refrigerant-side failure on an R-22 system is usually the point to replace rather than repair.
Repair or replace?
There is no single rule, but three checks cover most situations.
- Age against typical life. A repair on a 6-year-old system is almost always worth making. The same repair on a 16-year-old system buys little time.
- Repair cost times age. A common contractor shortcut multiplies the repair quote by the age of the system in years. If the result is more than about $5,000, replacement deserves a serious look. A $450 repair on a 9-year-old unit scores 4,050, so repair it. A $900 repair on a 14-year-old unit scores 12,600.
- What failed. Capacitors, contactors, igniters, and fan motors are routine repairs. A failed compressor, a leaking evaporator coil, or a cracked heat exchanger is expensive, and a cracked heat exchanger is a safety problem that takes the furnace out of service.
Typical service life
| Equipment | Typical life | Used in the calculator |
|---|---|---|
| Central air conditioner | 12 to 17 years | 15 years |
| Gas furnace | 15 to 20 years | 18 years |
| Heat pump | 10 to 15 years | 13 years |
| Ductless mini-split | 12 to 20 years | 15 years |
For a combined air conditioner and furnace, the calculator uses the shorter 15-year life, since most owners replace both when the air conditioner goes.
Tax credits and rebates in 2026
The federal energy efficient home improvement credit, which paid up to $2,000 toward a qualifying heat pump and up to $600 toward a qualifying furnace or central air conditioner, is not available for equipment placed in service after December 31, 2025. Legislation signed in July 2025 ended it. If your system was installed during 2025, you claim the credit on that year's return using Form 5695. A deposit paid in 2025 for a 2026 installation does not qualify.
What remains is local. Many electric and gas utilities pay rebates for high-efficiency equipment, and some states run their own heat pump incentive programs. Amounts and eligibility rules change often, so ask each bidder which rebates apply and confirm on your utility's website before signing. The calculator does not subtract incentives.
How to compare quotes
Get at least three written bids and check that each one states the same things.
- The brand, model numbers, capacity, and efficiency ratings of every piece of equipment.
- Whether a load calculation was done, and the result.
- What happens to the ductwork: reused as is, sealed, modified, or replaced.
- Electrical work, thermostat, condensate drain, pad, and line set, listed as included or excluded.
- Permit and inspection, and who pulls the permit.
- Removal and disposal of the old equipment and refrigerant.
- The manufacturer's parts warranty and the contractor's own labor warranty, in years.
The lowest bid is often the one that leaves something out. For help vetting the companies themselves, see our guide to finding the right contractors.
Budget for it before it fails
Because the failure date is roughly knowable, an HVAC replacement belongs in a planned reserve rather than on a credit card. Find the manufacture date on the nameplate, enter the age in the calculator, and treat the monthly figure as a bill you pay yourself. A system with five years left and a $12,000 typical replacement needs $200 a month. Waiting until two years remain raises that to $500.
HVAC is one of several systems on a clock. The annual maintenance cost estimator budgets for the roof, water heater, and appliances as well, and the home emergency fund calculator sizes the cushion for failures that arrive early.
Keep the paperwork
Four records from this project keep paying off for years.
- Model and serial numbers, and the installation date. Many manufacturers require you to register new equipment within a set window, often 60 to 90 days, to receive the full parts warranty.
- The contract and paid invoice. A full system replacement is a capital improvement. It adds to the cost basis of your home, which can lower the tax owed when you sell. The capital gains on home sale calculator shows what that is worth.
- The closed permit. Buyers and home inspectors ask for it.
- Service visits. A maintenance history supports warranty claims and reassures buyers that the system was cared for.
What the estimate leaves out
The calculator does not price boilers and hydronic heat, geothermal heat pumps, oil or propane furnaces, zoning systems, whole-house humidifiers or air cleaners, asbestos or mold remediation, structural changes, or financing costs. It also does not subtract rebates. Treat the result as a planning range to test contractor quotes against, not as a replacement for them.
Cost assumptions last reviewed November 2026.