There's rarely one "correct" answer. This tool weighs the factors contractors actually use — age, repair cost, replacement cost, repair history, and energy use — and shows how each one leans, so you can make the call with confidence.
Compare your repair quote against replacement bids from vetted local HVAC pros.
Find an HVAC ProCentral AC and heat pumps last ~15 years; gas furnaces ~20. Past about 75% of that, replacement moves up the list.
If a repair tops half the cost of a new system — or age × repair cost exceeds $5,000 — the math usually favors replacing.
We project both paths over 10 years, assuming the repaired system is eventually replaced when it reaches end of life, and factor in energy savings from a newer unit.
It's a useful starting point: if a repair costs more than half the price of a new system, replacement is often the better long-term value. But it works best combined with system age, repair history, and energy efficiency rather than on its own.
Multiply the system's age in years by the repair cost in dollars. If the result is over $5,000, the rule of thumb says lean toward replacement. A 12-year-old system with a $500 repair is 12 × 500 = $6,000, which favors replacing.
Central air conditioners and heat pumps typically last about 15 years, and gas furnaces about 20, with regular maintenance. Use our HVAC Maintenance Cost Calculator to see what upkeep costs.
If both are old, replacing them together often costs less than two separate jobs and keeps the system matched for efficiency. Compare with our HVAC Installation Cost Calculator.
This calculator provides a decision aid based on common HVAC rules of thumb and a simplified 10-year cost projection. It is not a substitute for an in-person inspection. Actual costs, system condition, and remaining life vary — get a written repair quote and at least one replacement estimate from a licensed local HVAC contractor before deciding.