Honest pricing · real ranges, no games
How much does a new AC unit cost in the St. Louis area?
Most O'Fallon and St. Louis-metro homeowners invest between $5,000 and $10,000 for an installed central air conditioner replacement. A 14.3 SEER2 single-stage system sits at the low end; an 18+ SEER2 variable-speed system can reach $12,500. Sizing, your indoor coil, and ductwork set the exact number, honest pricing starts with a free in-home visit.
Typical timeframe: Most AC replacements: one day, including old-unit haul-away
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By configuration
What does each AC tier cost?
Installed ranges for the O'Fallon / St. Charles County / greater St. Louis area. Your written quote depends on your home, the factors below explain what moves it.
Federal-minimum efficiency, dependable cooling at the lowest installed price
Longer, gentler cycles that wring more humidity out of St. Louis summers
Premium comfort and the best humidity control, with the lowest operating cost
Ranges are representative 2026 St. Louis-metro estimates, not quotes. Swiss Air confirms your exact price in writing after a free in-home evaluation, and explains every line item before any work begins. Updated July 20, 2026.
What changes the price
What affects your air conditioner price
Tonnage (Manual J sizing)
Bigger is not better. An oversized AC cools fast but shuts off before dehumidifying, a clammy house in a St. Louis July. Correct tonnage comes from a load calculation, not square footage.
The indoor coil match
The outdoor condenser and indoor evaporator coil must be a matched pair. If your coil is the old R-410A generation, it usually needs replacing with the condenser, a line item internet averages skip.
R-454B refrigerant transition
New ACs use R-454B under the 2025 federal phase-in. New-generation equipment costs more, and it's the main reason 'what my neighbor paid in 2022' no longer predicts your price.
Efficiency tier (SEER2)
Higher SEER2 costs more up front and less every summer. Two-stage and variable-speed tiers also dehumidify better, worth real money in our humidity.
Electrical & line set
Breaker sizing, disconnect, and the refrigerant line set between units may need updating to match the new equipment, verified on site, not from a prompt.
Permits & code
AC replacement requires a mechanical permit and inspection in most St. Louis-area jurisdictions. It's included in an honest installed price.
The honest part
Why exact pricing needs a home visit
- Correct tonnage requires a Manual J load calculation, oversizing causes the clammy-house problem in our humidity.
- Your indoor coil, line set, and electrical must be inspected to know what the job actually includes.
- Duct condition changes both comfort and price; we check it instead of assuming.
- Rebate eligibility depends on the exact matched-system ratings, verified at quote time.
- Ranges online, exact prices in writing after a free evaluation, no commission pressure, ever.
Seen an AI number?
Chatbots return national averages wearing a local label. They can't run a Manual J, see your ducts, or check your panel. Learn what AI misses, then get a real number.
Efficiency rebates and monthly payments
Qualifying high-efficiency ACs can earn Ameren Missouri rebates, and financing spreads the investment into monthly payments. We check current programs against the exact equipment in your quote.
Quick answers
Frequently asked
- How much does a new AC unit cost installed in St. Louis in 2026?
- Most installed central AC replacements in the O'Fallon and St. Louis metro run $5,000 to $10,000. Single-stage 14.3 SEER2 systems run $5,000 to $7,000; two-stage 16 to 17 SEER2 systems run $6,500 to $9,000; variable-speed 18+ SEER2 systems reach $12,500. Your exact price depends on sizing, coil match, and ductwork.
- Why did AC prices go up so much?
- Two federal transitions stacked: the SEER2 efficiency floor and the R-454B refrigerant phase-in that began in 2025. New-generation equipment simply costs more to build. Replacing on your schedule at today's price usually beats an emergency replacement later.
- Should I replace the indoor coil with the outdoor unit?
- Almost always, yes. The condenser and evaporator coil are engineered as a matched pair; mixing an R-454B condenser with an old R-410A coil isn't an option, and mismatches hurt efficiency and warranty coverage. A quote that skips the coil deserves a second look, bring it to us for a free review.
- My AC isn't cooling, repair or replace?
- It depends on age and the failure. A capacitor on a 6-year-old unit is a repair; a compressor or refrigerant leak on a 13-year-old R-410A unit usually favors replacement. Our repair-or-replace guide covers the honest math, and we'll tell you plainly which side your system lands on.
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