AC installation cost: central air by size, 2.5 to 4 tons, by state
A 3 ton system: about $6,300 to $7,400, typically $6,700. That's a central air conditioning system at 14 to 15 SEER, sized in tons, with the old one taken out, plus the contractor's overhead, profit and sales tax. New ductwork, electrical work and a new furnace are extra.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What it costs
| Job | Cost |
|---|---|
| A 2.5 ton system | $5,200 to $6,000 |
| A 3 ton system | $6,300 to $7,400 |
| A 4 ton system | $7,100 to $8,200 |
Totals include the contractor's overhead and profit (20%) and the state's average sales tax. Prices as of November 2026.
What’s in these numbers
Each total is a typical job, priced the way a contractor’s estimate is priced:
- A central air conditioning system in the size shown, 14 to 15 SEER, with the old system taken out.
- Overhead and profit: 20%, the standard markup on a contractor’s estimate.
- Sales tax on the materials, at the state’s average rate.
Not in them: new or changed ductwork, a new electrical circuit or disconnect, a new furnace or air handler, a pad or stand, a thermostat, and permits.
Tons and the size of the house
Air conditioners are sized in tons of cooling; one ton is 12,000 BTU an hour, so a 3 ton system is 36,000 BTU an hour. The code sizes cooling equipment from a load calculation of the house, ACCA Manual J, and picks the equipment by ACCA Manual S (IRC M1401.3). The load depends on the house’s size, insulation, windows, shade and climate, so floor area alone doesn’t set it.
The efficiency floor
Since January 1, 2023, a new split central air conditioner has to rate at least 13.4 SEER2 across the country, and 14.3 SEER2 (13.8 at 45,000 BTU an hour and up) in the Southeast and Southwest, and the Southwest adds an EER2 floor rated at 95°F outdoors (10 CFR 430.32(c)). A system that can’t meet its region’s floor can’t be installed there.
What moves the price
- Size. Bigger systems cost more.
- Efficiency. Higher-SEER systems cost more and use less power for the same cooling.
- Ducts and power. Leaky or undersized ducts, or a new circuit, add work.
- The furnace. A split system’s indoor coil sits on the furnace and uses its blower, so the furnace’s condition comes into it.
- Where you live. Pick your state in the box above.
Common questions
How much does central air cost to install?
About $6,300 to $7,400 for a 3 ton system with the old one taken out, typically $6,700.
How much is a 4 ton AC unit installed?
About $7,100 to $8,200, typically $7,500.
How much is a 2.5 ton system?
About $5,200 to $6,000.
Does a new AC need a new furnace?
Not always. The furnace’s blower moves the air for a split system, so its condition and size matter; the furnace replacement cost guide prices one. A heat pump heats and cools without a furnace, and a ductless mini split works without ducts.