Repair or replace your AC? The honest math

Short version: under 8 Florida years and a repair under $600, fix it. Past 12 Florida years with a four-figure repair on the table, replacement usually wins. Everything in between is math — and it’s math you can do yourself in five minutes. Here’s how.

The 1/3 rule, with real numbers

The industry shorthand: if a repair costs more than one-third of what a comparable new system would, lean replace — especially past 10 years of age. Under a third, repair usually wins. It works because it forces you to compare the repair against the actual alternative, not against zero.

Two worked examples from jobs we see every week:

• $450 blower motor, 6-year-old system. A comparable replacement runs about $8,500, so the 1/3 line sits at roughly $2,800. A $450 repair isn’t close. Repair — and don’t let anyone talk you out of it.
• $2,200 compressor, 13-year-old system. New system about $9,000, so the 1/3 line is $3,000. The repair technically passes… but you’d be putting a new heart in a body with 13 hard Florida summers on the coil, the ducts, and every motor. Age is the tiebreaker, and here it breaks toward replace.

Some techs use the $5,000 rule as a cross-check: multiply the system’s age by the repair cost. Under $5,000, repair; over, replace. That $450 motor at year 6 scores 2,700 — clear repair. The $2,200 compressor at year 13 scores 28,600 — not a close call. When both rules agree, trust them.

Florida years are not calendar years

Every rule of thumb you’ll read online was written for a national audience — systems that run hard four or five months a year. Yours doesn’t live there. A Southwest Florida system runs a 10-to-12-month cooling season, pulls moisture out of 80% humidity all day, and — anywhere near the Gulf — breathes salt air that corrodes coil fins and cabinet steel years ahead of schedule.

The practical conversion: a 12-year-old system in Naples or Cape Coral has the runtime hours of an 18-to-20-year-old system up north. So when a national article says “repair anything under 15 years,” subtract a third for Florida before you believe it. That’s why local systems typically last 10–15 years here instead of the 15–20 you’ll see quoted nationally — we broke that down in how long ACs last in Florida.

The decision table

Find your row. “Age” means Florida years, and “major repair” means compressor, evaporator coil, or a refrigerant leak repair — the $1,500+ tier from our Florida repair cost guide.

The efficiency math, at real FPL rates

Here’s where a lot of sales pitches go dishonest, so let’s do it straight. Say you have a 3-ton system that was SEER 13 new in 2012 and, with a decade of coil wear, performs closer to SEER 10 today. A new baseline system is SEER2 15.2.

• Old system: roughly 7,000–7,500 kWh a year of cooling in a typical SWFL home.
• New SEER2 15.2 system: the same cooling for roughly 4,700–5,000 kWh.
• At FPL’s residential rate (about 15¢/kWh), that’s roughly $350–$450 a year saved — call it $30–$40 a month. A higher-efficiency 16–17 SEER2 unit adds more; so does fixing leaky ducts at the same time.

Now the honest part: $400 a year does not pay for a $9,000 system. On efficiency alone, the payback runs well past a decade — anyone telling you a new AC “pays for itself in three years” is inflating something. What the efficiency savings actually do is tip a close call. If you’re facing a $2,500 repair anyway, the real cost of replacing is the difference — $6,500 — and $400 a year, plus a 10-year parts warranty, plus not paying for the next failure, makes that gap close fast. Which SEER2 tier is worth paying for in our climate gets its own treatment in our Florida SEER guide.

When repair clearly wins

• Young system, cheap part. A capacitor, contactor, or clogged drain line on anything under 10 years old. These are the majority of Florida service calls, and they’re same-day fixes.
• Major part still under warranty. A covered compressor or coil turns a $2,500 job into a labor bill.
• First failure on a well-maintained system. One bad part is a bad part, not a verdict on the whole unit.
• You’re selling the house within a year or two. A working repaired system usually beats spending five figures you won’t get back at closing.

When replacement wins

• A compressor or coil failure on an old-refrigerant system. R-22 systems, always. Older R-410A systems increasingly, as the AIM Act phase-down pushes recharge prices up every year.
• Repeated failures. Third service call in two summers means you’re paying replacement money on an installment plan — without getting the replacement.
• Past 12 Florida years with any four-figure repair. The 1/3 rule, the $5,000 rule, and our field experience all agree here.
• The system never cooled or dehumidified right to begin with. Wrong-sized equipment doesn’t repair its way to correct. Replacement is the fix — sized properly this time, the way we walk through on our AC installation page.

If the math lands on replace, the check doesn’t have to land all at once — financing options turn it into a monthly number you can weigh against those FPL savings directly.