AC Installation & Replacement in St. Louis, MO
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- Central AC replacement (3-ton), installed: $5,500–$10,000
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St. Louis at a glance
Why St. Louis needs cooling
St. Louis summers trap Mississippi Valley humidity against upper-80s and 90s heat, pushing heat indices past 100°F for stretches most Julys — while winters bring genuine freezes, so systems here work hard in both directions. The city's dense brick fabric holds daytime heat well into the evening.
Summer humidity: high (Mississippi Valley mugginess).
St. Louis cooling snapshot: America's brick city, retiring its window units at last.
AC installation costs in St. Louis
Whether you need a new central air conditioner installation, a like-for-like AC replacement or a heat-pump upgrade, local pricing reflects St. Louis's housing stock, labor market and permit requirements. The bands below are what surveyed, like-for-like quotes typically land at:
| System | Typical installed cost in St. Louis |
|---|---|
| Central AC replacement (3-ton), installed | $5,500 – $10,000 |
| Furnace + AC combo replacement, installed | $8,500 – $15,000 |
See the full national picture in our AC installation cost guide.
Popular systems in St. Louis
- Central AC + gas furnace
- Mini-splits for brick homes
- Heat pumps
St. Louis homes & buildings
St. Louis is America's great brick city: solid-masonry bungalows and flats across South City and Tower Grove, many still cooled by window units, alongside leafy county suburbs like Webster Groves and Kirkwood and newer growth in St. Charles County. Masonry homes without ducts make mini-split retrofits a fast-growing local specialty; homes with ducts typically run furnace-plus-AC combos.
Installing in St. Louis: what to know
City and county mechanical permits apply, and Ameren Missouri offers efficiency rebates on qualifying equipment and smart thermostats. Because heating and cooling loads are both serious, most replacements are quoted as furnace-and-AC pairs or heat pumps rather than cooling-only swaps. Drilling clean line-set penetrations through century-old brick is a skill worth vetting contractors on.
Research behind this St. Louis guide
Climate and population context is checked against NOAA climate normals and US Census QuickFacts. Certification guidance follows EPA Section 608. Prices are editorial market estimates, not quotes; a licensed contractor must assess the home before pricing.
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St. Louis, MO installation FAQs
My South City brick home has no ducts — what beats window units?
Ductless mini-splits, decisively. A head in the main living space and one per bedroom floor cools quietly and dehumidifies far better than window units fighting solid-masonry heat retention — and modern cold-climate heads can carry much of the winter too. Retrofitting full ductwork into solid brick walls is invasive and rarely worth it; mini-splits need only a small wall penetration.
Should I replace my furnace and AC together in St. Louis?
If both are 12+ years old, usually yes — they share a blower and installing them together saves duplicate labor, typically 10–20% versus two separate jobs. St. Louis's real winters mean the furnace half matters as much as the cooling; a matched high-efficiency pair (or a heat pump with gas backup) is the standard local recommendation.