Why AC Size Isn’t Just About Square Footage
So you’re shopping for an AC system and wondering, “Do I really need a 3-ton unit, or can I get away with 2.5?” Great question—and it’s more important than you might think.
AC size isn’t just about the square footage of your home. It’s about insulation, sun exposure, ceiling height, number of windows, even how many people live there. An undersized system will run non-stop and still leave you sweating. An oversized one? It'll cool too quickly and leave the air muggy. And guess what? Both will burn through your energy bill like a space heater on full blast.
If you want comfort and efficiency, you need to size it right—not just eyeball it.
The Basics: What "Tons" Really Mean
Quick HVAC 101: When we say “3-ton,” we’re not talking about the weight of the system. A ton in HVAC terms equals 12,000 BTUs per hour. So a 3-ton system can remove 36,000 BTUs of heat every hour from your home.
Use this rule-of-thumb calculator to get in the ballpark:
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1 ton = ~600 square feet (in a well-insulated home)
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2.5-ton system = ~1,500 square feet
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3-ton system = ~1,800 square feet
Need a starting point? The Goodman 3 Ton 15.2 SEER2 R-32 AC and Furnace System hits that sweet spot for average-sized homes in most U.S. climates.
But don’t stop there.
Beyond Square Footage: Real Factors That Matter
1. Climate Zone
If you’re in Texas or Florida, you’ll need more cooling power than someone in Michigan or Oregon. The U.S. is split into 8 climate zones, and each one has different sizing needs.
2. Insulation & Windows
If your attic is under-insulated or your windows leak air like a busted screen door, your AC is going to work harder than it should. Upgrade insulation before you oversize your HVAC.
3. Ceiling Height
Got vaulted ceilings or an open-concept layout? You’re moving more air than a standard 8-foot box of a house. That could bump you up half a ton.
4. Number of Occupants
Each human being adds heat. (Yes, even your kids while they’re sitting on the couch gaming.) Add about 600 BTUs per person.
Why “Bigger” Isn’t Always Better
Bigger might feel better—but not when it comes to AC. Oversized units short cycle. That means they cool your home too fast, then shut off before dehumidifying the air. What you end up with is a cold, damp house. Mold risk. Clammy skin. Higher energy bills.
Plus, constant cycling wears out components faster, meaning more repairs and a shorter lifespan.
Tools That Help You Get It Right
Want to get it exact? Use a Manual J load calculator (yes, that’s a real thing). There are free tools like:
Or, if you're like me, get close with the rule-of-thumb, check your insulation, and trust a system with a proven track record like the Goodman 3 Ton 15.2 SEER2 R-32 System.
Final Tip: Don’t Size Your AC in Isolation
Sizing your system means thinking about everything it connects to. That includes your ductwork, furnace, and how the air flows through your home. A top-tier condenser won’t help you if half your cooled air leaks into your attic.
That’s why buying a matched system like the Goodman unit—with an R-32 outdoor condenser, vertical coil, and high-efficiency 96% AFUE gas furnace—can make a real difference. You’re not guessing. You’re getting a package designed to work together.
Bottom Line from Mike
If you want your house to stay comfortable all year—without shelling out extra cash each month—sizing your AC system right is the most important decision you can make. Don't just go by what your neighbor installed. Do your homework. Use the tools. And when in doubt, size based on your actual conditions, not just square footage.
You’ll feel the difference. So will your wallet.
My Next Topic will cover: R-32 vs. R-410A: What’s the Difference, and Why Should You Care?
