HVAC Repair or Replace? Timing the $5,000–12,000 Decision
A dead compressor on a 15-year-old system is an easy replace call. The hard calls are the $800 repair on an 11-year-old system — fix it and hope, or put that money toward the inevitable? Here's the decision framework.
Quick answer: The 50% rule: repair cost × system age > 5,000 → replace (a $700 repair on a 10-year-old system = $7,000 → replace). AC life: 12–15 yrs · furnace: 15–20 · heat pump: 10–15. R-22 refrigerant systems: always replace (refrigerant costs more than the repair). Buy in fall/spring — off-season installs run 10–20% cheaper than July emergencies.
The rules that decide it
- 50% rule: repair × age > $5,000 → replace
- R-22 (Freon) system → replace; refrigerant is $50–100/lb and rising
- Cracked heat exchanger → replace (safety, not repairable)
- 2+ major repairs in 2 years → replace
- Under 8 years old → repair almost anything (warranty + life left)
System lifespans (when the math changes)
- Air conditioner: 12–15 years
- Furnace: 15–20 years
- Heat pump: 10–15 years (runs year-round)
- Ductwork: 20–25 years
- After year 12, efficiency decline means old 'working' systems cost more to run than new ones save
The timing game
Emergency July replacements pay sticker price with no negotiating room. Fall and spring are contractor slack season: better scheduling, real discounts, and time for a proper Manual J load calculation instead of a same-size swap. Plan the replacement on your schedule, not the system's.
Sizing: the most expensive mistake
Oversized systems short-cycle — cool fast, dehumidify poorly, wear out early. Undersized run forever and never catch up. The right size comes from a Manual J calculation (square footage, insulation, windows, orientation) — not from 'the old one was 3 tons'. Demand the Manual J; any contractor who won't do one is guessing with your $8,000.