How much does an HVAC technician cost in St. Louis? Based on BLS OEWS May 2024 wage data and RSMeans 2024 construction costs, here are real numbers — not the "$99–$975" ranges you get from lead-gen sites.
System sizing (Manual J load calculation) is critical — oversized systems short-cycle and undersized systems can't keep up.
Every price below is adjusted to St. Louis's labor market using a 1.08× city index applied to RSMeans 2024 national data. Labor hours assume standard conditions — add 15–40% for older homes, difficult access, or code catch-up.
| Job | Price Range | Hours | Permit |
|---|---|---|---|
|
Radiator Valve Replace (per unit)
TRV (thermostatic radiator valve) upgrade allows per-room temperature control.
|
$162–$486 | 1h | No |
|
Smart Thermostat Install + Configure
Ecobee vs Nest vs Honeywell T6 Pro. C-wire required for most smart thermostats. Add C-wire kit if missing.
|
$162–$486 | 1h | No |
|
Boiler Expansion Tank Replace
Waterlogged expansion tank = pressure relief valve weeping. Drain and check air charge first.
|
$216–$648 | 1h | No |
|
AC Refrigerant Recharge (leak check)
Low refrigerant = leak. Recharging without finding leak wastes money. UV dye test finds leak location.
|
$270–$810 | 2h | No |
|
UV Air Purifier Install (in-duct)
UV-C light kills bacteria/mold in coil area. Coil-mounted vs duct-mounted = different coverage.
|
$432–$1,296 | 2h | No |
|
Duct Sealing + Cleaning
HVAC systems lose 20-30% efficiency through duct leaks. Mastic sealant > tape long-term.
|
$864–$2,700 | 6h | No |
|
Multi-Zone Thermostat System
Requires zone board/controller. Each zone needs its own thermostat and damper.
|
$864–$2,700 | 4h | No |
|
Heat Pump Water Heater
Requires 7ft ceiling height minimum, 700+ cubic ft space, 30A/240V circuit. 3-4× more efficient than electric resistance.
|
$1,296–$3,240 | 4h | Required |
|
Heat Exchanger Replacement
Cracked heat exchanger = CO risk. If cracked, replace furnace - not worth repairing in most cases.
|
$1,620–$3,780 | 8h | No |
|
Air Handler Replace (indoor)
Coil condition drives decision - if evaporator coil leaking, full air handler often cheaper.
|
$1,620–$4,320 | 4h | Required |
|
Mini-Split Install (1 zone)
No ductwork required. Line set through wall, dedicated circuit. MrCool DIY vs MRCOOL Advantage = different install complexity.
|
$1,620–$4,320 | 6h | Required |
|
Zone Control Add (dampers + thermostat)
Adds motorized dampers in duct branches. Requires static pressure bypass to protect equipment.
|
$1,620–$4,320 | 8h | Required |
|
Attic Insulation - Blown-In (R-38)
CANNOT install over knob-and-tube wiring. Fiberglass vs cellulose: cellulose better at sealing, fiberglass less moisture risk.
|
$1,620–$4,320 | 6h | No |
|
ERV/HRV Fresh Air Install
ASHRAE 62.2 requires mechanical fresh air in tight homes. ERV recovers heat AND humidity.
|
$1,620–$4,320 | 8h | Required |
|
Electric Furnace/Air Handler Replace
No combustion, no flue - but requires 240V/60A circuit. Less efficient than heat pump.
|
$1,944–$4,860 | 6h | Required |
|
Condenser Unit Replace (outdoor)
Replace air handler at same time - mismatched efficiency ratings waste energy and void warranty.
|
$2,160–$5,400 | 4h | Required |
|
Gas Furnace Replace (80% AFUE)
80% vs 95% AFUE: 95% requires PVC flue (condensing), 80% uses B-vent. Check if existing flue is compatible.
|
$2,700–$6,480 | 8h | Required |
|
Gas Furnace Replace (95% AFUE)
Condensing furnace: PVC exhaust through wall or floor. Condensate line to drain required.
|
$3,240–$8,100 | 10h | Required |
|
Flex Duct Replacement (whole home)
Kinked flex duct = severe airflow restriction. Maximum 2 bends, no sags. Insulation R-8 required.
|
$3,240–$8,640 | 12h | Required |
|
Spray Foam Insulation - Attic
Closed-cell spray foam: best R-value per inch (R-6.5/in), also acts as air and vapor barrier.
|
$3,240–$8,640 | 8h | No |
|
Crawlspace Encapsulation
20-mil poly vapor barrier, drainage matting, dehumidifier. Transforms moisture problem permanently.
|
$3,240–$8,640 | 12h | No |
|
Central AC Unit Replace (2-5 ton)
Match refrigerant type (R-410A vs R-32 vs R-22). R-22 discontinued 2020 - if system uses R-22, full replacement needed.
|
$3,780–$8,640 | 8h | Required |
|
Boiler Replacement (natural gas)
Hydronic system: also check zone valves, expansion tank, circulator pump, backflow preventer.
|
$4,320–$10,800 | 12h | Required |
|
Heat Pump Replace - Split System
SEER2/HSPF2 ratings replace old SEER/HSPF. 15 SEER2 = minimum efficiency today.
|
$4,320–$9,720 | 8h | Required |
|
Mini-Split Install (3 zones)
Multi-zone: single outdoor unit, multiple heads. Head placement affects efficiency significantly.
|
$4,860–$10,800 | 14h | Required |
|
Geothermal Heat Pump (closed loop)
25-50 year lifespan on ground loop. Federal tax credit 30% through 2032.
|
$16,200–$37,800 | 40h | Required |
Prices: RSMeans 2024 × 1.08 (St. Louis index). Labor: BLS OEWS May 2024. Code: IRC Mechanical Code + NFPA 54 (gas). Required for furnace replacement, AC installation, and any gas line work. CO detector installation required by code.
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