What size AC do I need?
Your AC size — measured in tons — should come from a Manual J load calculation, not square footage alone. As a rough starting estimate, Florida homes often need around one ton of cooling per 400 to 600 square feet.
By that estimate, a roughly 1,500-square-foot home often lands near 3 tons — but that's only a planning figure. Humidity, insulation, window count and orientation, and ceiling height all move the real number meaningfully. The estimate gets you in the ballpark; a load calculation gets you the right answer. It helps to understand how air conditioning actually works first.
These are rough estimates only
The one-ton-per-400-to-600-square-feet range and the 3-ton example above are rough planning figures, not a quote or a guarantee. Two same-size Florida homes can need different tonnage. The only reliable way to size a system is a Manual J load calculation for your specific home.
Why square-footage rules of thumb fall short in Florida
Square footage ignores almost everything that actually drives cooling load. The same floor plan can need different tonnage depending on these factors — and Florida turns several of them up to maximum.
- Humidity: your system has to remove moisture, not just lower the temperature — a huge part of the Florida load.
- Sun & orientation: west-facing walls and big sunny windows add serious heat the afternoon AC has to fight.
- Insulation & ductwork: a leaky, poorly insulated home loses cooling and needs more capacity for the same comfort.
- Ceiling height: a vaulted ceiling means more air volume to cool than the floor area suggests.
- Coastal exposure: barrier-island and waterfront homes face extra heat and humidity loads near the water.
Why bigger is NOT better
It's tempting to think a larger AC just cools better. In practice an oversized system blasts the air cold fast, shuts off before it pulls out the humidity, then turns right back on — leaving you cold, clammy, and wearing the equipment out.
That on-off pattern is called short-cycling, and an oversized unit is one of its most common causes. Removing humidity takes runtime, so a system that satisfies the thermostat too quickly never runs long enough to dehumidify — which is exactly why a 72-degree Florida house can still feel damp. Learn more in AC short-cycling: why it happens.
Oversizing backfires in humid Florida
In our climate, humidity control is half the job. An oversized system actually makes comfort worse — clammy air, more wear, and higher bills — which is why "just go bigger to be safe" is the wrong instinct here.
What a Manual J load calculation includes
A Manual J is the industry-standard calculation that sizes your system to your actual home. Instead of a rule of thumb, it adds up the real heat gains and losses so the tonnage matches what your house genuinely needs.
- Square footage and ceiling height — the true air volume to cool.
- Insulation levels in the walls, attic, and floor.
- Window size, type, and which direction they face.
- Air leakage and ductwork condition.
- Local climate data plus occupants and major heat sources like the kitchen.
How Anna's sizes it right
We size systems to your home, not a chart. That means a proper load calculation and an honest recommendation — because an oversized or undersized system is uncomfortable no matter how good the equipment is.
Anna's is a woman-owned, local team serving Melbourne, Palm Bay, Viera, and the Space Coast. See what to expect from a Melbourne AC installation, or explore our air conditioning services.
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