Your AC or Furnace Just Quit: Repair or Replace?

Age times the quote, and where the line falls

Multiply the system's age in years by the repair quote in dollars. Over $5,000, start pricing replacement. Under it, the repair is usually the better money. A 12-year-old system facing a $500 repair scores 6,000, and that's the replace side of the line. The same $500 repair on a 7-year-old system scores 3,500, so you fix it and move on. For scale: common AC repairs run $150–$700, a central AC replacement runs $3,900–$12,500 installed, and a gas furnace replacement runs $3,500–$10,000. That gap is the whole argument. A few hundred dollars can buy years on a middle-aged system. The same few hundred, spent again every season on a system near the end of its life, only postpones a bill you're going to pay anyway. Nobody enjoys spending $3,900–$12,500 in August. Spending $500 over and over to get there is worse.

Have the nameplate and the callback count ready

You'll get a straighter answer on the phone if you can answer these first.

• Find the nameplate on the outdoor unit or the furnace cabinet. Write down the model number and the year it went in.
• How many service calls have you had in the past two years, and for what? Count them out loud before the tech arrives.
• Rule out the dumb stuff: tripped breaker, dead thermostat batteries, a filter packed solid, an outdoor disconnect somebody pulled and forgot.
• Write the symptom down in plain words. No cold air. No heat. Water on the floor.
• Dig up the paperwork. If the equipment or a major part is still under warranty, that changes which quote you're willing to accept.

The rule says nothing about what actually broke

The rule is a proxy for remaining value: an older system has fewer years left, so every repair dollar buys less time. Two problems. The threshold comes from an era when equipment cost less than it does now, and plenty of contractors argue it belongs higher against 2026 prices, so treat $5,000 as the start of a conversation and not a verdict. The bigger gap: the rule doesn't say a word about what actually broke. Swapping a capacitor and a contactor on a 9-year-old unit is routine wear, and that unit may run fine for years afterward. Put the same few hundred dollars toward a refrigerant leak on that same unit and you've bought time, not a fix. Leaks come back. Refrigerant got expensive. Run the multiplication, then ask what failed, not just what it costs, before you sign.

Why age hits harder than it used to

Central air conditioners typically last 15 to 20 years. Furnaces sit in the same general range, and maintenance history pushes any given unit toward one end or the other. Then there's the refrigerant problem. As of January 2025, manufacturers stopped building residential systems that run on R-410A. Your system is legal to run and legal to service. Nobody is coming to take it away. But production quotas are tightening under the phase-down, and HomeGuide now prices a recharge at $40 to $100 per pound installed, refrigerant and labor together. The newer refrigerants, R-454B and R-32, aren't backward-compatible, so there's no converting an old unit over to them. A 15-year-old system with a slow leak gets more expensive every summer it survives.

What replacement really costs in 2026

Replace only the side that failed and it's the smaller project: $3,900–$12,500 for a central AC — Angi prices a system at $3,900–$7,900, HomeGuide at $5,000–$8,300 for standard efficiency and $8,300–$12,500 for mid-range — and $3,500–$10,000 for a gas furnace, where HomeGuide says $3,500–$7,500 and up and This Old House $3,800–$10,000 installed. Do both at once and you're at $7,000–$20,000 for a home around 2,000 square feet. Tonnage moves that, and so do tired ducts. If the units share a blower and both are past their twelfth year, ask for combined pricing. One crew, one permit, one mess instead of two.

Don't sign anything at midnight

Expect a diagnostic or trip fee on the first visit, and the cost guides split on it: HomeGuide puts it at $75 to $200, Angi at $100 to $250. Many companies credit it toward the repair. After-hours calls bill at double or triple the regular rate. That's reason enough not to approve a replacement in the dark with a technician waiting on you. Pay for the visit. Have the tech stabilize it or shut it down safely. On a compressor or coil quote, one more $75-to-$250 diagnostic buys a second opinion worth having. And a price that dies when the truck leaves isn't a price.

Efficiency is a tiebreaker, not a reason

Go read the rating plate on your outdoor unit before anyone sells you on savings. Cooling is rated in SEER2 now, the standard adopted in 2023 and measured under conditions closer to how a system actually runs. Where you're starting from matters more than where you land. Trade a 10 SEER unit from the early 2000s for a 14.3 SEER2 system and cooling costs fall about 30% to 35%, on the order of $200–$400 a year for a 1,700-square-foot home in a moderate climate. An August bill in Phoenix stretches that further. Notice what's doing the work there: the twenty-year-old equipment you're leaving behind, not the last tenth of a point of rating you pay for. That's the argument for replacing a worn-out system, not for pulling a working one under ten years old.

Under ten years, past fifteen, and the callback count

Three things sort most of these calls: how old it is, what broke, and how often it keeps happening. Furnace repairs span $64–$1,475 in Angi's count of every furnace job; HomeGuide's single-part repairs are tighter, $100–$480 on gas and $100–$380 on electric.

• Repair wins under ten years old, first real failure, quote in that ordinary $150–$700 band.
• Replace wins past fifteen years, or when the quote names a compressor, evaporator coil, or heat exchanger.
• Refrigerant leak on an R-410A unit and they can't find it? Price replacement.
• Count the callbacks. Three or four failures across two seasons tells you where the rest of the parts are headed. Each one carries a trip fee.
• A cracked heat exchanger ends it. Combustion gases, shutdown on the spot.