Rule of thumb 1: the age-times-cost test
Multiply the age of the system by the cost of the repair. If the result is more than the cost of a new system, replacement usually makes more sense. A $600 repair on a 4-year-old system is an easy yes. The same repair on a 16-year-old system is a harder call.
Rule of thumb 2: the one-third rule
If a single repair costs more than about a third of a new system, and the system is past the middle of its expected life, get a replacement quote before you approve the repair.
Rule of thumb 3: what failed matters
- Capacitors, contactors, fan motors, drain issues, thermostats: almost always worth repairing.
- Refrigerant leaks in the coil: depends on age and refrigerant type. Older R-22 systems are expensive to recharge.
- Compressor failure on an older system: often the point where replacement wins.
Don't forget comfort and efficiency
Newer systems are significantly more efficient than ones installed 15 or 20 years ago, and variable-speed equipment handles humidity much better. In a climate like ours, that can mean noticeably lower summer bills and a less clammy house. If you've been fighting hot upstairs rooms or high indoor humidity, a replacement with a proper load calculation and duct check can fix problems a repair never will.
Get both numbers
The easiest way to decide is to ask the technician for both: the repair price and a replacement estimate. A good contractor will explain the trade-off without pressure. Request AC repair or a replacement estimate using the form.