Summary: Summary: The $5,000 rule says multiply the repair cost by the system's age in years: if the result exceeds $5,000, replace instead of repairing. A $600 repair on a 10-year-old system scores 6,000: replace. Beyond the rule, replace systems past 15 years needing major repairs, systems using phased-out R-22 refrigerant, and systems with cracked heat exchangers (a safety issue). Repair when the system is under 10 years old, the fix is minor, and efficiency is still reasonable.
The rule is simple arithmetic that captures a real economic insight: repair money spent on an old system has a short payback period because the system will need replacement soon anyway. Multiply the quoted repair cost by the equipment's age in years. Over $5,000: replace. Under $5,000: repair is usually rational.
Examples: a $400 capacitor replacement on an 8-year-old AC scores 3,200: repair, obviously. A $1,200 blower motor on a 12-year-old furnace scores 14,400: replace. A $900 repair on a 6-year-old heat pump scores 5,400: just over the line, which means get a replacement quote before authorizing the repair. The rule is a guide, not a law: use it to force the comparison, not to end the conversation.
Repair when the system is under 10 years old and the failure is a wear item: capacitors ($150 to $400), contactors ($200 to $450), thermostats ($150 to $400 installed), flame sensors and ignitors ($150 to $350), and condensate pumps ($200 to $450). These are the HVAC equivalent of brake pads: expected maintenance, not system failure.
Also repair when the system runs efficiently and the rest of it is healthy: a technician's assessment that the compressor, heat exchanger, and coils are sound carries weight. And repair when the budget genuinely cannot stretch to replacement: a $500 repair that buys two more years is rational finance, as long as you are saving for the replacement during those two years instead of being surprised by it.
Replace when the heat exchanger is cracked: this is a carbon monoxide safety issue, not an economic decision, and most technicians will red-tag the furnace on the spot. Replace when the system uses R-22 refrigerant (phased out; recharges cost $600 to $1,500 and rise yearly) and needs a major sealed-system repair. Replace when the compressor fails on a system past 12 years: the repair alone is $1,500 to $3,000 on borrowed time.
Replace when repairs are becoming annual: two $800 repairs in two years on a 14-year-old system is $1,600 spent on a system worth replacing, scoring 22,400 on the $5,000 rule. And replace when efficiency is terrible: a 25-year-old 10-SEER AC and 80-percent furnace cost hundreds more per year to run than modern equipment, which shortens the replacement payback substantially.
Old systems fail on the worst days: the compressor dies during the July heatwave and you pay emergency rates, or the furnace quits on the coldest night of the year. Emergency replacements cost 15 to 30 percent more than planned ones and force rushed decisions on equipment you will live with for 15 years. Planning the replacement on your schedule is worth real money.
There is also the refrigerant trap: R-22 systems needing recharges face $100-plus per pound and rising, with some contractors refusing to service them at all. And insurance and home-value angles: a 20-year-old HVAC is a negotiation point in every home sale and a non-renewal risk factor with some insurers. A planned replacement converts all of these from surprises into line items.
Get the repair quote in writing with the system's age and overall condition noted. Get a replacement quote at the same time: most companies quote both free, and comparing real numbers beats rule-of-thumb anxiety. Ask the technician directly: if this were your house and your money, would you repair or replace? Experienced techs answer this honestly and it is the most valuable sentence in the visit.
If you replace, do not repeat the mistake of buying on price alone: the load calculation, the installation quality items, and the contractor's reputation decide your next 15 years. If you repair, start the replacement fund the same month: price the future system now, save toward it, and replace on your schedule instead of the equipment's.
Data current as of October 2026. Sources: contractor pricing data and manufacturer guidance. Estimates only, not a quote. Always get multiple written quotes from licensed local HVAC contractors.