Quick answer
- Repair if the system is under 10 years old AND the repair is under 50% of replacement cost.
- Replace if the system uses R-22 (phased out) OR a major component (compressor, coil) has failed.
- Replace if the unit is 12-15+ years old — efficiency gains from a new SEER2 system often pay back the difference.
- The 2025 R-410A → R-454B refrigerant transition makes some major repairs financially worse than replacement.
- Always get the Manual J load calc on any replacement quote — don't size by what's already there.
The decision framework
Every repair-or-replace question reduces to five inputs. If you can answer these honestly, the right answer usually picks itself.
- How old is the system? (Find the data plate on the outdoor unit — the serial number includes a date code.)
- What's the quoted repair cost? (Get it in writing, with parts and labor itemized.)
- What would a replacement cost? (A real Manual J-sized quote, not a back-of-napkin guess.)
- What refrigerant does it use? (R-22 = retired, R-410A = phasing out, R-454B = current.)
- What's failing? (Capacitor or contactor = repair. Compressor or coil = harder math.)
The 50% rule
Industry rule of thumb: if a repair costs more than 50% of replacement, replace. The logic is that a major repair on an aging system buys you maybe 2-3 more years before the next major repair — at which point you've paid for the new system in repair bills.
When age alone tips the answer
Even with no failure, a 15-year-old SEER 10 unit (the federal minimum in 2010) is running at roughly half the efficiency of a current SEER2 16 unit. In Charleston, where AC runs 6-7 months a year, that delta shows up on every utility bill.
A worn-but-not-broken 15-year-old system can be a planned replacement on your schedule, versus an emergency replacement in July when it dies during a heat wave. Planning gives you time to get multiple quotes, evaluate rebates, and schedule install at convenience.
The refrigerant transition changes the math
Starting January 1, 2025, the EPA AIM Act prohibits new residential AC and heat pump systems with R-410A refrigerant — manufacturers can only build new equipment using R-454B or R-32. Existing R-410A systems are NOT illegal; you can keep running them. But the refrigerant supply for service is dropping and prices are climbing.
Practical impact: a major repair on a 10+ year old R-410A system (compressor replacement, coil replacement) often costs more than half of a R-454B replacement system. The math that worked in 2020 doesn't work in 2026.
When repair is the right answer
There are still plenty of cases where repair beats replacement. If your system is under 10 years old and the failure is a capacitor, contactor, fan motor, blower motor, or a minor refrigerant leak, repair is usually the right call.
The same goes for any system where the failure is in the duct system or the thermostat rather than the equipment itself — those repairs don't trigger the age/refrigerant math at all.
What to do next
If you've got an active repair quote in hand and you're unsure whether to take it, call us for a second opinion. Bring the quote — we'll walk through it with you, tell you what's reasonable and what's missing, and tell you what the replacement math actually looks like for your house.
Have a question about your system?
Talk to a real Charleston Lowcountry technician — a family-owned team with 30+ years of local experience that installs and services Carrier, Trane, Rheem, and more.