Homeowners often expect a simple answer: so many square feet per ton. That shortcut ignores most of what determines a home's actual cooling load, and in a humid climate the consequences show up as comfort problems rather than a house that is too warm.
What a load calculation accounts for
- Conditioned square footage and ceiling heights.
- Window area, orientation, glazing type, and shading — significant under Tallahassee's mature tree canopy.
- Insulation levels in walls and attic.
- Duct location, condition, and leakage, since ducts in a hot attic add real load.
- Air infiltration and how tight the house is.
- Occupancy and internal heat sources.
- Local design conditions rather than generic national assumptions.
Why oversizing is the common mistake
An oversized system satisfies the thermostat quickly and shuts off before it has removed much moisture. You end up with a cold, damp house, frequent on-off cycling, more wear on the compressor, and often uneven temperatures between rooms.
In North Florida, dehumidification depends on run time. Oversizing directly removes the run time the house needs.
Undersizing has its own problems
An undersized system runs continuously and still loses ground on the hottest afternoons. It is less common than oversizing, but it does happen — sometimes because the real problem is duct leakage or insulation rather than equipment capacity.
Why 'the same size as the old one' is not a plan
Matching the existing size assumes the existing size was right, which is often the very reason the home has never been comfortable. It also ignores changes since installation: new windows, added insulation, an enclosed porch, or a replaced roof.
What to ask for
Ask whether a load calculation is being performed, and ask what factors it accounted for. A company willing to walk your home, look in the attic, and measure is telling you something about how the rest of the work will go.