The Two Questions Every Homeowner Asks, Answered With Real Numbers
When an air conditioner starts struggling, every St. Louis homeowner lands on the same two questions: what's a new one going to cost me, and is it actually time, or can this one go another summer? Most websites dodge both. Here are the straight answers we give at kitchen tables across the metro.
What a New AC Costs, Installed
Here are our real prices for a standard 3-ton AC replacement in the St. Louis area. Equipment, labor, and installation included. (These are the same numbers our Instant HVAC Quote tool shows; final pricing is confirmed at your free in-home visit.)
*Two-Stage and Variable Speed pricing assumes the existing furnace is compatible. If a compatible furnace is not available, a full system replacement may be needed, which will affect pricing.
*Standard 3-ton installation. Larger homes, ductwork corrections, or electrical upgrades can move the number — which is why the in-home estimate is free.
Why such a wide spread? Four things set the price:
Size. Bigger homes need more cooling capacity (measured in tons) — and an oversized unit is just as bad as an undersized one. We measure; we don't guess from square footage alone.
Efficiency. Every AC carries a SEER2 rating — think of it as miles-per-gallon for cooling. Higher SEER2 costs more upfront and less every month, which matters over a St. Louis cooling season that runs from May into October.
Comfort features. Like furnaces, air conditioners come in single-stage, two-stage, and variable-speed versions. The higher tiers run longer, quieter, steadier, and pull more humidity out of the air, which is half the battle in a Missouri summer.
The installation itself. The indoor coil, refrigerant lines, electrical, permits, and the quality of the workmanship. Two identical units can perform completely differently depending on who installs them; sizing, airflow, and refrigerant charge are where corners get cut.
One 2026 note: new air conditioners now use a new-generation refrigerant (R-454B) required by federal regulation. It's better for the environment, but the transition pushed equipment prices up roughly 10–20% versus a couple of years ago. That's industry-wide, not any one company, and it's one more reason an aging system facing a big repair is worth replacing on your schedule rather than in a heat wave.
How Long Do AC Units Last?
A new central air conditioner gives you 12 to 15 years. In St. Louis, humid 95-degree stretches work a system hard, so where yours lands in that range depends mostly on maintenance:
- Years 1–12: the prime years. With an annual cooling system check, most units cruise through this stretch with only minor repairs.
- Years 12–15: watch closely. Efficiency slips, parts wear together, and repairs start arriving in clusters.
- Past 15: borrowed time. It can happen — we've seen 20-year-old units still limping along — but every summer is a coin flip, and older refrigerants make repairs increasingly expensive.
An annual cooling system check is the single cheapest way to reach the high end of that range. (Preferred Partner Plan members get theirs included, plus priority scheduling when summer gets busy.)
When to Replace an AC Unit
Here's the rule of thumb we use ourselves:
- Under about 10 years old + a minor repair → fix it. The system has plenty of life left.
- 12–15+ years old + a major repair (compressor, coil, refrigerant leak) → replace. Sinking $1,500–$3,000 into a system near the end of its life usually just delays — and adds to — the inevitable.
- In between? Weigh the repair cost against the system's remaining years. If the repair costs more than a third of replacement and the unit is past its 12th birthday, replacement almost always wins the math.
Warning signs it's time, regardless of the math:
- Cooling bills climbing year over year with no change in habits
- Back-to-back repairs — two service calls in the same summer is the classic tell
- Rooms that never get cool, or a system that runs constantly on hot days
- An R-22 (Freon) system — that refrigerant is no longer produced, and even older R-410A systems now face rising repair-refrigerant costs
Should You Replace the Furnace at the Same Time?
If your furnace is a similar age, it's worth pricing the combination. The AC's indoor coil sits on top of the furnace and shares its blower, so replacing both at once avoids paying labor twice, guarantees the two are matched for efficiency, and usually costs meaningfully less than doing them separately a year or two apart.
Having an AC and furnace that are compatible is a major concern. For example; a two-stage furnace with a single-stage AC will only get you the benefits for heating, and not cooling. (Comparing furnace options? See our furnace stages guide.)
How to Get a Real Number
Online averages are a starting point, not a price. An accurate quote requires knowing your home's size, ductwork, insulation, and electrical — which is why estimates on new AC installations from Air Comfort Service are always free. A comfort specialist measures your home and quotes a good-better-best set of real options, so you see the actual price gaps instead of guessing.
Financing is available, and if your home struggles to stay cool, attic insulation is often the cheapest comfort upgrade you can pair with a new system — it lets a right-sized AC do less work.
Having an AC and furnace that are compatible is a major concern. For example; a two-stage furnace with a single-stage AC will only get you the benefits for heating, and not cooling. (Comparing furnace options? See our furnace stages guide.)
Talk It Through with Air Comfort Service
We've been installing and servicing air conditioners across the St. Louis metro since 1969. We're family-owned, factory-certified, and honest about whether your system needs replacing at all. If a repair is the smarter call, that's what we'll tell you.
FAQs
A: For a standard 3-ton installation in the St. Louis area, our installed prices run from $8,959 for dependable single-stage cooling to $13,980 for a whisper-quiet variable-speed system, with two-stage comfort at $10,790. (Two-stage and variable-speed pricing assumes your existing furnace is compatible; if not, a full system replacement may be needed, which affects pricing.) Equipment-only prices you see online exclude the coil, labor, and installation that a real replacement includes.