Central air conditioner replacement cost in St. Louis, MO
Installed, 3 ton (outdoor unit + matching coil)
A typical central AC (3 ton (outdoor unit + matching coil)) costs about $4,700 installed in the St. Louis area, 1% above the national figure, because HVAC technicians here earn a median $30 an hour against $29 nationally.
Prices by size in St. Louis
| Size | Low | Typical | High | National typical |
|---|---|---|---|---|
| 2 ton (outdoor unit + matching coil) | $3,150 | $3,550 | $4,600 | $3,500 |
| 3 ton (outdoor unit + matching coil) | $4,100 | $4,700 | $6,200 | $4,650 |
| 4 ton (outdoor unit + matching coil) | $5,500 | $6,050 | $7,800 | $6,000 |
| 5 ton (outdoor unit + matching coil) | $6,700 | $7,500 | $9,050 | $7,400 |
Local labor: what HVAC technicians earn here
| Hourly wage | St. Louis metro | United States |
|---|---|---|
| 25th percentile | $24 | $23 |
| Median | $30 | $29 |
| 75th percentile | $38 | $37 |
The St. Louis market
The City of St. Louis Building Division issues plumbing permits only to licensed plumbing contractors certified by the city, and mechanical permits only to city-certified licensed mechanical contractors. No homeowner route is stated. The plumbing fee schedule prices a water heater as a fixture at $10, plus a $30 application fee. For homes, mechanical permits carry a $25 application fee plus $40 for each furnace, condensing unit or combination furnace and condensing unit. Heat pumps are not named. After approval you print the permit and schedule inspections through the STL City Permits dashboard. EIA found furnaces are main heat in 76% of Missouri homes and central air serves 83%. St. Louis County, a separate government from the city, has its own permit office, and so do the Illinois counties in the metro.
Condenser replacement is routine in St. Louis. Summers are hot and humid, so ask how the new system handles moisture. An oversized unit cools fast and shuts off before it dries the air. Ask for a load calculation and a matched coil, and ask whether the line set will be reused. When the furnace under the coil is old, price the pair together. Get the tonnage and SEER2 rating in writing.
Permits in St. Louis
| Permit for this job | Yes for furnaces and boilers; AC/condensing units inferred from fee lines; heat pump not named (source) |
|---|---|
| Fee | Plumbing: $30 application fee + $10 per fixture (water heater listed). Mechanical (R1-R3 residential): $25 application fee + $40 per furnace, $40 per condensing unit, or $40 per combination furnace/condensing unit. |
| Who can pull it | City-licensed contractor only (City plumbing contractor or mechanical contractor license); homeowner route not stated |
| Inspection | Yes (scheduled through STL City Permits dashboard after approval) |
Rebates in Missouri
HEAR: announced, not open yet. HOMES: announced, not open yet. Source: Missouri DNR Division of Energy, checked October 13, 2026.
What these programs cover, and other states
Other systems in St. Louis
- Gas tank water heater
- Gas tankless water heater
- Gas furnace
- Heat pump (ducted, outdoor unit + air handler)
Central air conditioner cost in other metros
Sources
- City of St. Louis: Mechanical permits
- City of St. Louis: Plumbing permits
- City of St. Louis: Plumbing permit fees
- City of St. Louis: Mechanical permit fees
- Missouri DNR: IRA home energy rebates
- EIA, 2020 RECS: Highlights for space heating in U.S. homes by state
- EIA, 2020 RECS: Highlights for water heating in U.S. homes by state
- EIA, 2020 RECS: Highlights for air conditioning in U.S. homes by state
- BLS OEWS May 2025, St. Louis, MO-IL (49-9021 HVAC mechanics and installers)
- DOE Residential CAC & Heat Pumps Direct Final Rule TSD (Dec 2016), Table 8.2.30, split AC coil-only (2015$; 4-ton interpolated)