How we built these ranges
The figures below come from repair quotes and paid invoices that homeowners and contractors in the St. Louis metro shared with us between spring 2025 and summer 2026. They are not national averages, and they exclude memberships and multi-item projects where individual line pricing was not itemized.
Treat them as a sanity check, not a price list. A quote noticeably outside these ranges is worth a second opinion; it is not automatically wrong, because access, equipment brand, and parts availability all move the number.
Diagnostic and service call fees
Standard business-hours diagnostic fees in the metro run $89 to $150, and most companies apply that fee toward the repair if you approve the work. Evening, weekend, and holiday rates commonly run $150 to $300, and a few shops charge time-and-a-half labor on top.
Some companies waive the diagnostic for maintenance plan members, which is where those $150 to $250 annual plans start to pay for themselves if you own older equipment.
Common repairs and typical installed prices
Run capacitor $180 to $350. Contactor $180 to $300. Hard-start kit $150 to $300. Thermostat replacement $200 to $600 depending on whether it is a basic programmable or a communicating model. Flame sensor or ignitor $200 to $400. Condenser fan motor $450 to $850. Blower motor $600 to $1,300, with ECM variable-speed motors at the high end.
Sealed-system and heat-exchange work is a different tier: refrigerant leak search and repair $500 to $1,500, evaporator coil replacement $1,400 to $2,600, compressor replacement $1,800 to $3,200, and heat exchanger replacement $1,500 to $2,800 where the part is still available. Once you are in this tier on equipment older than 12 years, ask for a replacement quote alongside the repair quote.
What actually moves the price in this market
Access is the biggest local variable. Attic air handlers in newer St. Charles County subdivisions and crawlspace units in older south county homes add labor hours that a basement installation does not. Refrigerant type matters too: R-22 systems carry a materials premium and R-410A is now also rising as the industry transitions to A2L refrigerants such as R-454B.
Parts warranty status is worth checking before you approve anything. Many manufacturers cover parts for ten years when the system was registered at install. If yours was, you may be paying labor only, which can cut a coil replacement roughly in half.
Getting a comparable second quote
To compare quotes fairly, ask each company for the failed part name and number, whether the part is under manufacturer warranty, the labor hours assumed, and whether the diagnostic fee is credited. Without those four items you are comparing totals, not scope.
On repairs above roughly $1,500, a second opinion is normal and reasonable. Any contractor who reacts badly to that request has told you something worth knowing.
Frequently asked questions
Should I buy a maintenance plan?
They generally make sense for equipment over eight years old or for households that want priority scheduling in July. For newer systems under warranty, the value is mostly the waived diagnostic and the reminder to change filters.
Why are after-hours HVAC rates so much higher in summer?
Demand during heat advisories exceeds available technicians, and overtime labor costs more. If the house is safe and you can manage overnight, a next-morning appointment usually saves $100 to $200.
Is a flat-rate or hourly HVAC company cheaper?
Flat rate gives you price certainty before work begins; hourly can be cheaper on quick jobs and more expensive on complicated ones. Ask which model the company uses before the technician arrives.
Sources and further reading
Price ranges in this guide come from quotes and invoices shared with STL Home Pros by St. Louis area homeowners and contractors. Technical and climate references are listed below.
About the author
Nick Cascani is a New York native who has called St. Louis home for the last few years. He believes getting professional home service should be simple and convenient, and he writes these guides to help local homeowners make confident decisions about their HVAC, plumbing, and foundation projects.
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