Enter your system's age, the repair quote and what a replacement would cost. We check the two rules of thumb contractors use and show where each one would flip.
Updated October 2026 · Free · No sign-up
Repair or replace your HVAC system?
What the two rules of thumb say
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Rule or measure
Your numbers
Points to
These are rules of thumb, not guarantees. The 50% rule is Fixr's guideline: replace when a repair costs more than half the price of a new system, especially on an older unit. The age-times-cost rule (age in years × repair quote over $5,000) is a contractor rule of thumb, not a standard. The defaults are example values (the Fixr average compressor repair and a mid-range replacement), not your quote. A covered warranty, a second opinion, or a failing furnace on the same system can change the answer.
How the math works
The 50% rule. Compare the repair quote with half of the replacement price. Fixr's guideline is to replace when the repair costs more than half of a new system, especially on an older unit.
The $5,000 rule. Multiply the system's age in years by the repair quote. A result over $5,000 means replacement deserves a serious look. This is a contractor rule of thumb, not a standard.
Age and lifespan. Fixr says most AC units are designed to last 10 to 15 years, and ENERGY STAR flags central AC older than 10 years as a replacement candidate when it needs frequent repairs and bills are rising. We show remaining life for context but do not use it in the verdict.
If both rules agree the verdict is clearer; if they disagree, it is a judgment call. For example, a $1,550 compressor repair on a 9-year-old system passes the 50% test against an $8,000 replacement (19%) but age times quote is $13,950, so the rules split.
What this calculator assumes
Rules of thumb, not guarantees. They ignore warranty coverage, refrigerant type, your climate, and whether other parts are near the end of their life.
Example defaults. The $1,550 repair is Fixr's average compressor repair and $8,000 sits inside the $5,500 to $12,000 range for central AC replacement in our guide. Neither is your quote; replace them with your own.
Quote totals. Include the diagnostic fee and any surcharge in the repair figure, and use an installed replacement price that includes the coil and permits.
Fixr's guideline: if a repair costs more than half the price of a new system, especially on an older unit, replace it instead. It is a rule of thumb, not a guarantee, and the repair quote and replacement price you use change the answer.
What is the $5,000 rule for HVAC?
Multiply the system's age in years by the repair quote. If the result is over $5,000, replacement deserves a serious look. It is a contractor rule of thumb, not a standard, but it penalizes both an expensive repair and an old unit.
How long does a central air conditioner last?
Fixr notes most AC units are designed to last 10 to 15 years, and ENERGY STAR flags central AC older than 10 years as a replacement candidate, particularly when it needs frequent repairs and energy bills are rising. Climate, maintenance and installation quality all move the real figure.
What if the two rules give different answers?
That means a judgment call. Check whether the part is under a manufacturer warranty, whether the coil and furnace are also old, how often the system has been repaired, and get a second opinion on any quote over $1,000. Our AC repair cost guide walks through a case where the rules disagree.
Does this calculator work for furnaces and heat pumps?
The 50% and age-times-cost rules come from AC repair guidance, so they fit central AC best. For a furnace or heat pump, lifespan and replacement price differ; enter figures for your equipment and treat the result as a starting point for a conversation with your contractor.
