The 5,000 Rule
The most widely used rule of thumb for the repair-vs-replace decision: multiply the age of the system (in years) by the estimated repair cost. If the result exceeds $5,000, replacement is usually the better financial decision.
Example: Your 12-year-old AC needs a $450 capacitor replacement. 12 × $450 = $5,400. That's above the threshold — worth considering replacement, especially if the system has had other recent repairs.
Example: Your 5-year-old AC needs the same $450 repair. 5 × $450 = $2,250. Well below the threshold — repair makes sense.
The 5,000 Rule is a starting point, not a final answer. Other factors matter too.
Age: The Most Important Factor
Central air conditioners typically last 15–20 years with proper maintenance. In Chicago's climate — hot, humid summers and cold winters that stress the equipment — 15 years is a reasonable planning horizon.
If your system is under 10 years old and the repair is under $500, repair almost always makes sense. If the system is over 15 years old, any significant repair is worth weighing against replacement — you're investing in equipment that may fail again within a few years.
Refrigerant Type
If your system uses R-22 (Freon), replacement refrigerant is expensive — often $100 to $200 per pound — and increasingly difficult to source. A system that needs a refrigerant recharge due to a leak is almost always better replaced than repaired when it uses R-22.
Systems using R-410A are still serviceable, but new equipment no longer uses R-410A. If your R-410A system needs a major repair, factor in that replacement parts will eventually become harder to source as the installed base ages.
Repair Cost by Component
Capacitor ($150 to $350): Almost always worth repairing on any system under 15 years old. One of the most common AC repairs.
Contactor ($150 to $300): Same as capacitor — inexpensive repair, worth doing on any reasonably young system.
Fan motor ($300 to $600): Worth repairing on systems under 12 years old. On older systems, apply the 5,000 Rule.
Refrigerant leak repair + recharge ($400 to $1,500+): Depends heavily on where the leak is. A leak in the service valve is cheap to fix. A leak in the evaporator coil may require coil replacement — at that point, replacing the whole system is often more cost-effective.
Evaporator coil replacement ($800 to $2,000): On a system over 10 years old, replacing the coil alone rarely makes sense. The condenser is the same age and will likely fail within a few years. Replace the full system.
Compressor replacement ($1,200 to $2,500+): The most expensive single repair. On any system over 8 years old, replacement is almost always the better choice. A new compressor in an old system is expensive, and the rest of the equipment is still aging.
Efficiency: The Hidden Cost of Keeping an Old System
A 15-year-old AC system is likely rated at 10–13 SEER (roughly 9.5–12.4 SEER2 equivalent). A new 16 SEER2 system uses about 25–35% less electricity for the same cooling output. In Chicago, that's roughly $100 to $200 per year in savings on a typical home.
When you factor in the efficiency gains, the true cost of keeping an old system is higher than the repair bill alone. A new system pays for itself faster than most homeowners expect when you account for both energy savings and avoided future repairs.
When to Repair
- System is under 10 years old
- Repair cost is under $500
- No history of repeated repairs in the past 2–3 years
- System uses R-410A or newer refrigerant
- System is properly sized for the home
When to Replace
- System is 15+ years old
- Repair cost × age exceeds $5,000
- System uses R-22 refrigerant
- Compressor has failed
- Evaporator coil needs replacement on a system over 10 years old
- Multiple repairs in the past 2–3 years
- System is oversized or undersized for the home
Get a Second Opinion
If a contractor recommends a major repair on an older system, it's worth getting a second opinion — or at minimum asking them to walk you through the repair-vs-replace math. D's Air will give you an honest assessment. We don't push replacement when repair makes sense, and we don't recommend repairs that don't make financial sense for the homeowner. Call (773) 940-0965.