This is the most expensive question a homeowner gets asked in the middle of a 112-degree week, usually under pressure, usually by someone who earns more on one answer than the other. Here's how to run it yourself in five minutes.
Input 1: real age, not installed-in age
Arizona systems age faster. A unit that would see twelve to fifteen years in a mild climate typically sees ten to fourteen here, and a rooftop package unit in full sun is at the low end of that.
Under 8 years, repair almost always wins. Over 14, replacement usually does. The 8-to-14 window is where the rest of the inputs decide it.
Input 2: the 50% rule
If the repair costs more than half of what a comparable new system costs, replacement generally wins. A $2,400 compressor swap on a 13-year-old unit that would cost $8,000 to replace is a bad trade — you're paying 30% of a new system for a machine with maybe three summers left.
Input 3: what refrigerant it uses
R-22 systems are the clear-cut case. The refrigerant is phased out, priced high, and any leak repair on that system is throwing money at a machine that can't be economically recharged in a few years. If you have R-22 and a significant repair, replace.
Newer R-410A and R-454B systems don't carry that penalty.
Input 4: how long you're staying
Selling in two years? A correct, documented repair keeps the house sellable without pre-paying for efficiency you'll never use. Staying ten? The efficiency difference between a 2010 10-SEER unit and a modern system is real money in a Valley summer — often $40 to $90 a month in the peak months.
What you should get before you decide
Insist on three things from whoever is quoting you, and take the quote away overnight if you want to.
- Photos and measured readings showing the failed part
- A flat written repair price and a written replacement price, side by side
- A load calculation for the replacement — not a like-for-like tonnage guess