AC Replacement Cost in 2026: What Homeowners Actually Pay

Marcus D., Master HVAC & appliance technician — St. Louis, MO

An AC replacement is not one price. It is equipment, labor, refrigerant, electrical, permits, and whatever the ductwork needs. The tables below give installed ranges for the St. Louis area in 2026. They assume a standard split system with a matched indoor coil and a line set under 25 feet. They do not include duct replacement, panel upgrades, or major surprises. Use them to sanity-check a quote, not to pick a contractor by price alone.

Installed cost by size

System size	Installed range (standard efficiency)
1.5 ton	$3,500–$5,500
2 ton	$4,000–$6,000
2.5 ton	$4,500–$6,800
3 ton	$5,000–$7,500
3.5 ton	$5,500–$8,200
4 ton	$6,000–$9,000
5 ton	$7,000–$10,500

These ranges are for a straight AC with a matched coil or a full system with a furnace. A heat pump sits higher, often $1,000 to $3,000 more for the same size. A full system — outdoor unit, indoor coil, furnace, line set, thermostat — runs $7,000 to $15,000 typical, and can exceed $20,000 with ductwork. The size you need comes from a load calculation, not from the old unit’s label.

What efficiency actually buys

Efficiency tier	Typical price premium	Honest savings in St. Louis
14.3–15 SEER2 (standard)	Base	Baseline
16 SEER2	Add $600–$1,200	About 8–10% cooling energy; often $50–$150 per season
18 SEER2	Add $1,200–$2,500	About 15–20% cooling energy; $100–$250 per season
20+ SEER2 variable-speed	Add $2,000–$4,000	About 20–30% cooling energy; comfort and humidity gains are the real reason

The payback on high efficiency is long. Going from 14.3 to 16 SEER2 might save $50 to $150 a year. The premium is $600 to $1,200. That is a five- to fifteen-year payback on a machine that may last 12 to 15 years. Buy high efficiency for quiet operation, better humidity control, and lower peak demand if you have the budget. Do not buy it because a salesman promises it will pay for itself.

Coil-only vs full system

A coil-only replacement runs $1,200 to $2,500 installed. It is tempting when the outdoor unit still works. The problem is matching. An old outdoor unit and a new coil may not be an AHRI-matched pair. Mismatched equipment can lose efficiency, lose capacity, and void the warranty on one or both parts. If the outdoor unit is more than 10 years old, a full system is usually the better long-term call. If the outdoor unit is young and the coil is the only failure, a matched coil is fine. Ask for the AHRI certificate or the match number.

Line items on a real invoice

Outdoor condensing unit and matched indoor coil
Line set (standard 25 ft; extra $15–$30 per foot)
Refrigerant charge and evacuation
Electrical disconnect and whip
Thermostat (basic included; smart thermostat $150–$350)
Permit ($150–$500)
Labor and haul-away
Pad or wall bracket
Condensate drain and float switch

Ductwork is the wild card. A quote may include a “duct inspection,” but that is not a duct design. If the static pressure is high or the ducts are undersized, you may need $1,500 to $5,000 in duct repairs. A crushed flex run in the attic can kill airflow to a room. A disconnected duct can pull attic air into the supply. Neither shows up until someone gets in the attic and looks.

Refrigerant transition note

New equipment is moving to R-454B and other lower-GWP refrigerants. Older R-410A units are being phased down. That has made R-410A refrigerant more expensive and sometimes harder to get. A recharge on an older R-410A system can run $150 to $300 per pound in some markets, and a system may hold several pounds. If you are facing a large refrigerant leak on an old R-410A unit, that repair can push the decision toward replacement. The new refrigerant is not a drop-in swap. Do not let anyone tell you they can “convert” an old system cheaply.

Rebates, tax credits, and red flags

Rebates and tax credits exist, but they vary by utility, state, and efficiency tier. Check current local utility programs and the federal 25C tax credit rules before you sign. Never trust a quote that guarantees a rebate amount. The contractor does not control the program, and the rules change. A quote that promises a specific rebate without checking your eligibility is a red flag.

Other red flags: a quote that skips the load calculation, a quote that does not list the model numbers, a quote that will not pull a permit, a quote that pressures you to sign the same day, and a quote that is 40 percent below the others with no explanation. Cheap HVAC usually means cut corners on line set, electrical, or ductwork. Those corners show up later.

STOP: Refrigerant is under pressure. Do not loosen flare nuts, valve cores, or service port caps. Liquid refrigerant can freeze skin and displace oxygen in a small space. Only a licensed tech with gauges and recovery equipment should touch the sealed system.

STOP: The outdoor unit and air handler have mains voltage. Do not open the electrical compartment or pull the disconnect with the power on. Shut off the breaker at the panel before anyone services it.

STOP: Do not add refrigerant yourself from a store-bought can. It is illegal without a Section 608 certification, and you can overcharge the system or introduce air and moisture. That turns a small repair into a compressor replacement.

Calculators and guides give ranges and rules of thumb from field experience — they are not a diagnosis of your system. When a guide says stop, stop: gas, refrigerant, and mains electrical work belong to licensed pros. Get two or three written quotes before signing anything.

Marcus D.

Master HVAC & appliance technician — St. Louis, MO

Marcus has spent 20+ years diagnosing and repairing HVAC systems, appliances, plumbing and electrical problems in St. Louis homes. Call a Tech Last is where he writes down what he tells his own family before they call anyone.