Central air conditioning: how it works and what it should cost

Central air conditioning — an outdoor condenser, an indoor coil on the furnace or air handler, and the home’s duct network — cools about two-thirds of American homes. Since January 2023, new units must meet SEER2 minimums that depend on where you live: 13.4 SEER2 in the North, 14.3 in the Southeast and Southwest (the Southwest adds EER2 requirements for hot-dry performance). Our SEER2 guide unpacks what the ratings mean on a utility bill.

Two facts save buyers the most money. First, ducts matter as much as the box: typical duct systems leak 20–30% of conditioned air (ENERGY STAR figures), so sealing and insulating ducts often beats paying for two extra SEER2 points. Second, sizing is a calculation, not a rule of thumb — a Manual J load calculation is the industry standard, and an oversized unit short-cycles, dehumidifies poorly and dies younger. Use our BTU calculator pages for a first estimate, then insist on the real math.

Frequently asked questions

How much does replacing central AC cost?

Indicative 2026 ranges: $4,500–$8,500 installed for a straightforward like-for-like swap of a 2–3.5 ton system, more with duct repairs, coil replacement or high-efficiency two-stage/variable equipment. These are market reference ranges, not quotes — regional labor and refrigerant transition (R-454B/R-32 equipment) move prices.

Should I replace central AC with a heat pump?

If your furnace is also aging, often yes: a heat pump replaces both, qualifies for the federal 25C tax credit (up to $2,000) plus state and utility rebates, and modern cold-climate models heat reliably well below freezing. If your furnace is young and gas is cheap in your area, an AC-only swap can still pencil out.

By state and by size

State rules and climates: all 50 states. Sizing: BTU by square footage. Brands: Carrier, Trane, Lennox, Goodman, Midea.

Other equipment types: Heat pump · Mini-split · Window AC · Portable AC.