Cost data reviewed August 2026. Sources listed at the foot of this page.
Sizing, and why bigger is not safer
Air conditioners are sized in tons, where one ton equals 12,000 BTU of cooling per hour. The rule of thumb is 500 to 600 square feet per ton, or about 20 to 25 BTU per square foot — with the range running from 16 BTU per square foot in a mild climate with good insulation to 30 in a hot climate or a leaky house.
The instinct to round up is a costly one. An oversized system cools the air to the thermostat setpoint quickly and shuts off before it has run long enough to pull humidity out. You end up with a house that is cold and clammy, a compressor that short-cycles, and equipment that wears out years early. Undersizing is uncomfortable; oversizing is uncomfortable and expensive.
| Home size | Typical tonnage | Installed cost |
|---|---|---|
| 1,000 sq ft | 1.5 – 2 | $4,500 – $7,000 |
| 1,500 sq ft | 2.5 – 3 | $6,000 – $8,500 |
| 2,000 sq ft | 3.5 – 4.5 | $7,000 – $11,500 |
| 2,500 sq ft | 4.5 – 5 | $8,500 – $13,500 |
| 3,000 sq ft | 5+ | $10,000 – $16,000 |
The square-foot rule is a sanity check, not a design method. A proper Manual J load calculation accounts for your climate zone, insulation R-values, window area and orientation, air infiltration, ceiling heights and internal gains. It is what a good installer runs, and if a contractor sizes your system by glancing at the old unit’s nameplate, that is a reason to get another quote. Use this calculator to know whether their answer is in the right neighbourhood.
Efficiency: where the payback actually is
SEER ratings run from 13 to 26. Higher-efficiency equipment costs substantially more — standard efficiency systems run $5,000 to $8,300, mid-range $8,300 to $12,500, and high-efficiency systems $14,000 and up.
Whether the premium pays back depends almost entirely on how many hours a year the unit actually runs. In Phoenix or Houston, where cooling runs eight months, a high-SEER system can recover its premium. In Seattle or Minneapolis, where it runs for a few weeks, it will not — you would be paying for efficiency you never use. Ask your installer for the estimated annual operating cost at each tier rather than accepting the SEER number as self-evidently worth it.
Ductwork is the line item to ask about first
Minor duct modifications run $300 to $1,500. Full replacement runs $1,400 to $5,600 or more. On a job where the equipment is $6,000, that is the difference between a routine replacement and a project.
Old ducts often leak 20 to 30 percent of conditioned air into attics and crawlspaces. Putting an efficient new system on leaky ductwork wastes much of what you paid for. If your ducts are original to an older house, ask for a duct leakage test before you choose an efficiency tier — sealing existing ducts is frequently a better return than upgrading the equipment.
Getting comparable quotes
HVAC quotes are unusually hard to compare because scope varies so much. Ask every contractor for: the calculated tonnage and the Manual J to back it; the equipment make, model and SEER; whether the air handler or furnace coil is being replaced; the line set and electrical work included; the ductwork scope; the permit; and the labor warranty separate from the manufacturer’s parts warranty. Two quotes $4,000 apart usually differ on three of those.
Common questions
What size AC do I need for a 2,000 sq ft house?
Typically 3.5 to 4.5 tons, depending on climate, insulation and window area. At 22 BTU per square foot that is 44,000 BTU, or about 3.7 tons — so a 3.5 or 4-ton system. Have a Manual J calculation done to confirm before buying.
How much does it cost to replace a central air conditioner?
A standard-efficiency system runs about $5,000 to $8,300 installed for most residential sizes. Mid-range efficiency is $8,300 to $12,500, and high-efficiency systems start around $14,000. Ductwork, if needed, is on top of that.
Is a higher SEER rating worth the money?
It depends on your cooling hours. In hot climates with long seasons, higher SEER can pay back through lower running costs. In mild climates it usually does not. Ask for estimated annual operating cost at each tier rather than deciding on the SEER number alone.
Can I replace just the outdoor unit?
It is generally a poor idea. The outdoor condenser and indoor coil are matched as a system, and pairing a new condenser with an old coil typically means you do not get the rated efficiency and may void the warranty. If the existing coil is old, replacing both is the sound choice.