Should I repair or replace my AC?

Age and repair cost are the two real inputs. A young AC with a failed capacitor or contactor is an easy repair call — cheap fix, years of life left. An AC in its teens facing a compressor replacement is a much closer call, because you'd be spending a large fraction of a new system's price on a unit whose other components (coils, blower) are aging on the same timeline.

Efficiency is the tiebreaker worth knowing about: a unit from the early 2010s or older is meaningfully less efficient than current equipment, so replacement sometimes pays part of itself back in lower cooling bills — not usually enough to justify replacing a healthy unit early, but worth factoring in when the age and repair cost are already close to the replace threshold.