Tools & Calculators

Repair or replace? Run the actual math.

Your system just died or a tech quoted you a repair. Contractors use two real rules to make this call — the 50% rule and the $5,000 rule. Enter your numbers and see both, transparently, including when they disagree.

years
How old is the current unit?
$
What the technician quoted to fix it.
$
Pre-filled with a typical range — enter your own quote if you have one.
Your verdict

50% rule
$5,000 rule

How this is computed. 50% rule: repair cost ÷ replacement cost — 50%+ leans replace. $5,000 rule: system age × repair cost — over 5,000 leans replace. Both are widely used contractor heuristics, not laws of physics; we show the math so you can judge it yourself. Typical lifespans (source: Bryant, cross-checked against Carrier): central AC 12–20 years, gas furnace 15–30 years, heat pump 10–20 years — actual life depends heavily on maintenance, climate and run-hours. Typical replacement-cost midpoints (source: HVACProjectCost.com, AC and furnace; heat pump average from EnergySage) are pre-fills only — always use your own quote when you have one. Full formulas in our methodology.

Common questions

What is the 50% rule for HVAC repair vs. replacement?

If the repair estimate is 50% or more of the cost to replace the whole system, most HVAC contractors say replace rather than repair. A $2,000 repair on a system that would cost $5,000 to replace (40%) leans repair; the same $2,000 repair on a $3,500 system (57%) leans replace.

What is the $5,000 rule for HVAC?

Multiply the age of your system in years by the repair cost in dollars. If the result is over 5,000, replacement is usually the better financial call. A 12-year-old system needing a $500 repair scores 6,000 (over the line); a 3-year-old system needing the same $500 repair scores 1,500 (well under it) — the same repair bill means something different depending on the system's age.

What if the 50% rule and the $5,000 rule disagree?

It happens, especially on newer systems with an expensive repair, or older systems with a cheap one. When the two rules point different directions, treat it as a genuine toss-up: weigh how many years of service you'd realistically get from the repair against a new system's warranty and efficiency, and get a second opinion on the diagnosis before committing either way.

Is it ever worth repairing a system that's past its typical lifespan?

Sometimes — if the repair is minor (a capacitor, a blower motor) and cheap relative to replacement, an old-but-otherwise-healthy system can still be worth one more repair. The risk is stacking repairs: a system already past 75% of its typical lifespan is statistically more likely to need another repair within a year or two, which is what both rules are really trying to price in.