HVAC Repair vs Replace Calculator
Enter your system’s age and the repair quote to see whether fixing or replacing wins on the math.
Runs entirely in your browser — your numbers never leave this page.
How it works
HVAC contractors use three rules of thumb — this tool runs all three against your quotes:
- The 50% rule: if one repair costs more than half of a new system, replace. You’re buying a warranty and a fresh lifespan instead of patching a dying one.
- The $5,000 rule: multiply system age by the repair cost. Over $5,000 → replace. A $600 repair on a 10-year-old furnace scores $6,000: replace.
- The age rule: ACs past ~10 years and furnaces past ~15 are on borrowed time — even a cheap repair just buys months.
- The efficiency gap: an old 80% AFUE furnace wastes 20¢ of every heating dollar versus 96%+ new. On a $2,200 bill, a 20% gain saves ~$440/year.
- Repair anyway when: the system is young, the fix is minor and isolated, and you’ve had fewer than 3 repairs in 3 years.
Frequently asked questions
What is the 50% rule for HVAC?
If a single repair costs more than 50% of a full replacement, replacing is the better investment — you get a new warranty and full lifespan.
What is the $5,000 HVAC rule?
Multiply the system’s age by the repair cost. If the result tops $5,000, replace rather than repair.
How long do HVAC systems last?
Typically 10–15 years for air conditioners and 15–20 years for furnaces, depending on maintenance and climate.
How much does HVAC replacement cost?
Roughly $3,800–$7,500 for central AC and $2,600–$6,200 for a furnace, installed — size, brand and efficiency rating move the number.
Can a cracked heat exchanger be repaired?
No — it cannot be safely welded or patched. A cracked heat exchanger means shutting the furnace down (carbon monoxide risk) and usually replacing it.
Should I replace R-22 equipment?
Yes, if it needs refrigerant work — R-22 is phased out, so recharges are expensive and getting worse every year.
Does a new system really cut energy bills?
Upgrading from 80% to 96% AFUE cuts heating waste dramatically; expect 15–35% lower bills depending on how old the old unit is.
Is a maintenance contract worth it?
Annual tune-ups ($75–$200) catch small failures early and many manufacturers require documented maintenance to honor warranties.
Repair or replace a 12-year-old AC with a $900 fix?
Age × repair = $10,800 — over the $5,000 line, and past the 10-year AC threshold. Two rules say replace.
Should I get multiple quotes?
Always — at least three. Replacement quotes for the same job routinely differ by 30% or more.