Calculator
Put in the quote you were actually given. The tool does the arithmetic the trade uses, and shows its working.
Nothing is sent anywhere. The maths runs in your browser.
| Typical life for a central air conditioner | 12 to 17 years |
| Age × repair quote (the $5,000 rule) | 14 × $1,800 = $25,200 |
| Years of typical life left | 3 years |
| This repair costs, per remaining year | $600 per year |
You are looking at a replacement, not a repair. Get a real installed price from a local crew before you spend anything on the old system.
Get replacement quotes →The rule is simple enough to do in your head at the kitchen table: multiply the system's age by the repair quote, and if the result clears 5,000, lean towards replacing. A 15 year old furnace with a $400 repair scores 6,000 and says replace. A 5 year old one with the same fault scores 2,000 and says fix it.
It works because it captures the two things that actually matter at once. An old system will need the next repair sooner, and an expensive repair on an old system is money spent on equipment that is going to be scrapped anyway.
Where it fails is at the edges. It has no opinion on a 20 year old system with a $50 repair, which it scores at 1,000 and calls a repair, even though you are one failure away from an emergency replacement in the middle of a heatwave. And it says nothing about what a new system would cost you, which is the other half of the decision.
That is why this calculator also prints the cost per remaining year. It is the number that survives both edge cases.
Every other calculator of this kind will happily tell you that a new system costs some specific figure, and then compare your repair to it. We do not, for a reason worth stating plainly: installed HVAC pricing varies by more than a factor of two depending on your ductwork, your electrical panel, access, permits, and which contractor you call. A national average is not a number you can make a decision with, and dressing one up as a personalised estimate would be misleading.
So the tool asks for the repair quote you were actually handed, and does arithmetic on that. If you want the other half of the comparison, get one replacement quote. The 50 percent rule is the standard test once you have both numbers: if the repair costs more than half of a full replacement, replace.
R-22 refrigerant was banned from production and import in the United States on 1 January 2020. Systems installed around 2010 or earlier are the ones likely to be charged with it, and they cannot be topped up cheaply any more. Reclaimed R-22 is the only legal supply and it is priced accordingly.
This matters because of what it does to the arithmetic. A leak on an R-22 system is not one repair. It is a recharge now, and another recharge when the same leak keeps leaking, on equipment nobody makes parts for. If your system is old enough to hold R-22 and the diagnosis involves refrigerant, the honest answer usually shifts to replacement even when the $5,000 rule has not been crossed.
Ask the technician which refrigerant your system uses. It is printed on the data plate on the outdoor unit, so it is a question with a checkable answer.
The typical life figures this tool uses are national planning numbers, and they assume a climate that works the equipment hard. A great deal of the East Bay does not. A condenser in San Leandro or Alameda may run a few dozen hours in a cool summer, against many hundreds for the same unit in Sacramento or Phoenix, and run hours are what wear it out.
The practical effect is that a 15 year old air conditioner near the shoreline can be in genuinely better condition than its age suggests, and worth repairing where the rule says otherwise. The offsetting local factor is salt air, which corrodes outdoor coils near the water. Rinsing the condenser with a hose a couple of times a year is free and it measurably slows that down.
If your system is close to the line, the age on the data plate is less informative than what the technician can see on the coil.
Every row below is this calculator's own output, so you can see how the inputs move the answer.
| System | Age | Repair quote | Verdict |
|---|---|---|---|
| Central AC | 6 years | $600 | repair |
| Central AC | 14 years | $1,800 | replace |
| Gas furnace | 18 years | $900 | replace |
| Heat pump | 12 years | $2,200 | replace |
FAQ
Multiply the age of the system in years by the cost of the repair in dollars. If the result is more than 5,000, replacing the system is usually the better use of the money. A 10 year old system with a $600 repair scores 6,000 and leans replace, while a 4 year old system with the same repair scores 2,400 and leans repair.
It depends almost entirely on the size of the repair and the refrigerant. A cheap repair such as a capacitor or a contactor is worth doing at any age. A repair involving the compressor, the evaporator coil, or a refrigerant leak on an older R-22 system usually is not, because the next failure is close behind and parts for that generation are getting harder to source.
It can, in one specific situation: the system still works, it is old enough that you expect failures, and you would rather pay a predictable monthly amount than a surprise four figure bill. It is a poor fit if the system is already broken, because pre-existing faults are the standard exclusion in every plan. Read what the plan excludes before the coverage amount, since that is where the differences actually are.
Twelve to seventeen years is the usual planning range for a central air conditioner, fifteen to twenty for a gas furnace, and ten to fifteen for a heat pump, which runs year round and therefore accumulates hours faster. These are rules of thumb rather than guarantees, and run hours matter more than calendar age.
For anything in four figures, yes. Diagnoses genuinely differ, and so do prices for the same part. Ask each contractor to write down the specific component they are replacing and why, because two quotes for different repairs are not comparable and that is the most common way people overpay.
Related guide:
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