AC Installation in St. Louis, MO

AC installation in St. Louis comes down to one number: how much heat your house gains on a 95-degree afternoon. We calculate that load first and pick equipment second. Copying the old unit's size is the shortcut that leaves homes humid, uneven and noisy.

What should a complete AC installation quote list?

A written quote for a new central air conditioner should itemize each of these, so two bids can be compared line by line.

• The load calculation result and the tonnage chosen from it
• Outdoor condenser and matched indoor coil or air handler, with model numbers
• Pad, line set, electrical disconnect and wiring to the unit's rated circuit
• Condensate drain with a float safety switch
• Recovery of the old system's refrigerant, since EPA's Section 608 rules prohibit intentionally venting it
• Evacuation, refrigerant charge, airflow check and start-up test
• Permit, haul-away of the old unit, and what is excluded

A quote that skips any of these lines is not wrong yet, but it is incomplete. Ask what the blank means: included, excluded or not needed. Exclusions are where two similar totals come apart.

Which type of air conditioner fits your house?

Most St. Louis homes with a furnace and ducts take a split system: an outdoor condenser paired with an indoor coil. A heat pump uses the same layout but also heats, which suits homeowners who are also weighing a furnace swap; see heat pump installation. Homes with no ducts, such as brick bungalows with radiators or new additions, often suit ductless mini splits better than a retrofit duct system.

DOE's 2023 standards set a minimum of 13.4 SEER2 for split air conditioners under 45,000 Btu/h in the North region, which includes Missouri. Higher ratings cost more upfront and save on bills only if the system runs long hours. A house with shade and tight windows may never recover the difference.

When a home needs a first-time or full AC installation

A full installation, rather than a swap, comes up in three situations. The house never had central air, the existing ducts cannot carry cooling airflow, or an addition or finished basement has changed the load. Within the City, the median house dates to 1938 (ACS via Neilsberg), and across St. Louis County 53 percent of homes predate 1970 (ACS 2020-2024). Older houses often cool with window units because no duct path ever existed.

In those homes the question is routing before equipment. Closets, soffits and basement ceilings can carry a small-duct or retrofit run, and where nothing fits, a ductless system is the alternative.

How is a new air conditioner sized?

A new air conditioner is sized with a room-by-room heat load, not a square-foot rule. ACCA's Manual J calculates the load, Manual S matches equipment to it, and Manual D checks the ducts can move the air. The National Renewable Energy Laboratory (NREL) notes that oversizing is common and causes short cycling, which wears parts and leaves humidity behind.

St. Louis is in ASHRAE Climate Zone 4A, mixed-humid, so moisture removal matters as much as temperature. An undersized unit runs forever on the hottest days. An oversized one never runs long enough to dry the air.

How does the installation go, step by step?

The sequence below is the order a careful install follows, though exact timing depends on scope.

1. Walk the house, measure it and run the load calculation.
2. Review duct condition, the return path, the pad location and the electrical panel.
3. Agree on equipment and give you a clear, upfront quote before work starts.
4. Recover the old refrigerant, disconnect and remove the old unit.
5. Set the new pad and condenser, then fit the coil and seal the plenum.
6. Run the line set, the drain and the wiring.
7. Pull a vacuum, charge the system and measure airflow and temperature split.
8. Walk you through the thermostat, filter and what to watch for.

What does a new AC cost in St. Louis?

Fixr, a cost-estimating site, reports about $6,000 for a 3-ton central AC in 2026, with most homeowners paying $5,000 to $12,000. That is a national market figure, not our quote. Fixr puts labor at $500 to $2,500 and new ductwork at $1,400 to $6,000 (page updated January 28, 2026).

If the AC comes bundled with a furnace, Angi's 2026 data puts a combined system at $4,755-$11,888 in the metro, with labor at $75-$150 per hour. Ameren Missouri's 2026 chart lists no rebate for a plain AC, only for heat pumps and mini splits, so an AC-only quote should not assume one.

Four things move the price:

• Tonnage and efficiency rating
• Ductwork repair, sealing or replacement
• Electrical work, such as a new disconnect or breaker
• Access, including an attic coil or a tight side yard

What do the permit, inspection and license rules say?

Missouri has no statewide HVAC license, so cities and counties set the rules. St. Louis County requires a mechanical permit to install or replace an air conditioner, and the contractor should hold a St. Louis County mechanical license. The City of St. Louis requires a mechanical contractor licensed in the City under Ordinance 70800 and charges a $25 permit application fee. Ballwin and Creve Coeur add their own contractor and inspection steps, so check with the local building office.

Ask any contractor, including us, for the license number that applies to your address, and ask who pulls the permit. Put the answer in the written quote.

How do you care for a new air conditioner?

Change the filter on the schedule the installer gives you, keep two feet of clear space around the condenser, and rinse cottonwood fluff off the coil each spring. Save the model and serial numbers and ask for the manufacturer's registration steps in writing. A first AC maintenance visit before the next summer keeps small drifts from becoming service calls.

Why Kenan Corporation for a new AC installation

Kenan Corporation holds 4.6★ from 29 Google reviews as of October 2026, and the habits below are the ones reviewers describe.

• Calculation before equipment. We run a load calculation before sizing, and we explain the result so you can challenge it.
• Replacement only when it makes sense. A Google reviewer, Ms. O., had a rusty, leaking AC that no longer reached temperature, and a new system was the honest answer. Where a repair works, we say so first.
• Options laid out. Candice F. writes that Kenan is great at giving options, which is how an install quote should read.
• A phone that works at night. The business is open 24 hours, and a dead system in July can get a same-day visit when the schedule allows.

We install in Florissant, Ferguson, Hazelwood and Jennings, all within about 20 to 25 minutes of our base near Spanish Lake in normal traffic. See Florissant, Ferguson and Hazelwood for local details.

Where we install air conditioners

Times below are normal-traffic drives from Broadhead Lane, offered as planning figures rather than promises.

• Jennings, about 20 minutes: the city building department issues the mechanical permit, and a new owner or tenant also needs an inspection and occupancy permit.
• Florissant, about 20 minutes: about 18,000 houses were built from 1947 to 1980, so a first full-system replacement on checked ducts is the usual job.
• Ferguson, about 20 minutes: Code Compliance takes the construction permit that covers mechanical work through an online portal.
• Hazelwood, about 25 minutes: the city's inspection office works under the 2021 International Mechanical Code and the Fuel Gas Code.
• Richmond Heights, about 35 minutes: 43 percent of homes predate 1940, so a retrofit starts with a closet, soffit or basement ceiling that can carry ducts.
• Creve Coeur, about 40 minutes: the 1970s built the most homes here at 23 percent, and finished basements and additions change the cooling load.
• Chesterfield, about 50 minutes: about 42 percent of units date to the 1980s and 1990s, and city code lets a separate mechanical permit be filed.
• O'Fallon, about 50 minutes: permit applications ask for the licensed subcontractor's name and license number, so settle that before the install date.
• Wentzville, about 65 minutes: the city requires a contractor license renewed each February 28, and permits run through its online portal.

Call first for the farther towns to confirm scheduling.