HVAC Repair vs. Replacement Cost in St. Louis, MO (2026)
Deciding between repairing an aging furnace or AC system and replacing it outright is one of the biggest HVAC decisions St. Louis homeowners face. This guide lays out 2026 repair and replacement pricing across the metro so you can make the call with real numbers. Start with our St. Louis HVAC hub for the full local picture, or get matched with St. Louis HVAC pros for quotes today.
By Homeowner Henry · HVAC · Published September 7, 2026 · 8 min read
Repair Costs at a Glance
Furnace repairs in St. Louis typically run $175-$700 depending on the part, with igniter and blower motor issues on the lower end and heat exchanger problems on the higher end.
AC repairs follow a similar range, from $150 for a simple capacitor swap up to $1,400 for major compressor work, so the specific failure matters more than the system's age alone.
Full Replacement Costs Across the Metro
A full central AC replacement (3-ton system, typical for a St. Louis single-family home) runs $5,200-$8,900 installed in 2026, while furnace replacement runs $4,300-$8,200 depending on BTU output and efficiency tier.
Replacing both systems together often saves on labor compared to doing them separately, typically landing in the $8,500-$16,000 range for a full swap.
The 50% Rule and System Age
A common industry guideline is that if a repair costs more than 50% of a full replacement, replacement is usually the better long-term value, especially for systems already past 12-15 years old.
St. Louis's long cooling season also means newer, higher-SEER2 equipment can pay back faster in energy savings here than in milder climates.
Financing and Rebates in the St. Louis Area
Ameren Missouri offers rebates for qualifying high-efficiency furnace, AC, and heat pump installations, which can offset several hundred dollars of replacement cost.
Many local contractors also offer 0% or low-interest financing plans for replacements over $5,000, which is worth asking about during your quote.
Permits for Replacement Work
Full system replacement almost always requires a mechanical permit whether you're in the City of St. Louis or St. Louis County, and your contractor should pull this on your behalf.
Skipping the permit can create problems at resale, since inspectors and buyers' agents often check for permit history on major mechanical work.
Typical cost ranges
| Furnace repair | $175 - $700 |
| AC repair | $150 - $1,400 |
| Central AC replacement (3-ton) | $5,200 - $8,900 |
| Furnace replacement | $4,300 - $8,200 |
| Full HVAC system replacement | $8,500 - $16,000 |
| Heat pump installation | $6,800 - $13,500 |
Ranges are general estimates gathered from homeowner-reported quotes, not an offer or a quote for your project.
Common questions
How do I know if I should repair or replace my HVAC system?
If the repair costs more than 50% of a full replacement and your system is over 12-15 years old, replacement is usually the better value in the long run.
How much does a full HVAC replacement cost in St. Louis?
Replacing both an AC unit and furnace together typically runs $8,500-$16,000 installed as of 2026, depending on equipment tier and ductwork condition.
Are there rebates for new HVAC systems in St. Louis?
Ameren Missouri offers rebates for qualifying high-efficiency equipment installed by participating contractors, which can lower total replacement cost.
Do I need a permit for a full HVAC replacement in St. Louis?
Yes, both the City of St. Louis and St. Louis County require a mechanical permit for full system replacement.
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