Repair or Replace? The 7-Year Math for Phoenix AC Units
Phoenix heat ages an AC unit faster than anywhere else in the country. Here's the math we actually run — age, repair cost, efficiency, and your power bill — before we tell you which way to go.
Every AC company has a "rule" for repair vs. replace. Most of them are built to sell you a system. Here's the one we use, with the numbers behind it, so you can run it yourself before anyone shows up.
Why 7 years, not 15
The brochure says an air conditioner lasts 15 to 20 years. That number comes from national averages. A unit in Ohio runs maybe 800 hours a summer. A unit on a Tempe roof runs 2,500+ hours, in 110°+ ambient heat, with the sun beating on the cabinet. Everything inside — compressor windings, capacitors, motor bearings, coil fins — ages on a different clock.
In our experience, most Valley systems hit the point where repair costs start climbing at around year 7. That doesn't mean replace it at 7. It means from 7 on, every repair deserves the math below. We service plenty of 18-year-old units and keep them going; the owner just needs to know what they're paying for.
The four numbers
1. Age. Under 7, repair almost always wins. 7 to 12, run the math. Over 12, a major repair (compressor, coil, refrigerant leak) usually loses.
2. Repair cost vs. replacement cost. The common shortcut is the 50% rule: if the repair is more than half the cost of a new system, replace. We use a stricter version — multiply the repair cost by the unit's age. If that's more than the price of a new system, replace. A $1,500 compressor on a 10-year-old unit is $15,000 in "age-dollars," which is more than most replacements cost. Same repair on a 4-year-old unit is $6,000 — repair it.
3. Efficiency gap. A 10-year-old 13 SEER unit versus a new 15.2+ SEER2 heat pump — the new one uses roughly 20–30% less electricity for the same cooling. On a Valley summer bill of $300–$400 a month, that's real money. We'll estimate it for your house, not from a chart.
4. Refrigerant. If the unit uses R-22 (most units made before 2010), any refrigerant repair is expensive and getting worse. That alone tips a lot of decisions.
Signs the math is about to change
- Repairs two summers in a row
- Runs constantly on hot afternoons and still can't hold the set temp
- Uneven rooms — one side of the house cooks
- Power bill creeping up with no change in use
- Rust or oil stains on the outdoor unit (refrigerant leak)
- A tech who condemned it — get a second opinion; ours are free
What "replace" should actually mean
A replacement isn't just a new box. Done right, it includes:
- A load calculation on your actual house. Not "same size as the old one." Oversized units short-cycle, leave humidity in the air, and wear out faster.
- A matched indoor coil. Replacing only the outdoor unit with a mismatched coil cuts efficiency and can void the warranty.
- Permit pulled with your city. Every Valley city requires one for a changeout.
- SRP rebate paperwork if you're an SRP customer — see our rebate post.
What we tell you
Both numbers. The repair, all-in. And the replacement, all-in, with the estimated bill savings. Then you decide. If the repair is the right answer, we say so — even when a replacement would be a bigger ticket for us. That's the whole reason Patriot Air exists.
Questions people ask
My AC is 15 years old and works fine. Should I replace it anyway?+
No. Replace it when the math says so, not the calendar. Keep it maintained, budget for a replacement, and don't let anyone scare you into it.
Should I replace just the outdoor unit to save money?+
Usually not. A mismatched indoor coil cuts efficiency and can void the manufacturer warranty. We'll tell you when it's worth it and when it isn't.
How long does a replacement take?+
Most residential changeouts are one day. Rooftop package units are typically a morning.
Do you offer financing?+
Yes, on approved credit. We'll also apply any manufacturer rebates or utility rebates you qualify for.