The rule of thumb, and its limits
A common starting point in a climate like ours is somewhere between 400 and 600 square feet per ton of cooling. A 2,000 square foot house therefore lands somewhere around 3.5 to 5 tons before anything else is considered.
That range is wide because the shortcut ignores everything that actually varies: insulation, window area and orientation, ceiling height, air leakage, duct location and how many people live there. Use it to sanity-check a proposal, not to specify one.
What a load calculation adds
A Manual J calculation works from the building itself — envelope, glazing, orientation, infiltration, internal gains and duct losses — and produces a number for your house rather than for a house of that size.
Two houses with identical footprints can differ by a full ton. A 1990s house with single glazing and ducts in a hot attic is a different problem from a well-sealed recent build with the same floor area.
Why oversizing is the common mistake
Installers round up instinctively, and matching the previous system's tonnage perpetuates whatever error was made last time.
An oversized system short-cycles: it hits the set temperature fast, shuts off, and restarts soon after. That means poor dehumidification, uneven room temperatures, more compressor wear from repeated starts, and a house that is cold and damp at the same time.
The ducts set the ceiling
A correctly sized system on undersized returns or leaky supply runs will not deliver its rated capacity, and no amount of equipment quality fixes that.
If a replacement proposal does not mention the duct system at all, ask what was found when it was inspected.
Nothing here replaces a proper measurement. The free site visit is the point at which we confirm every figure — call (912) 858-3737 or book one below.
Further reading:What a new AC costs in Savannah in 2026Getting HVAC right in a new buildSingle-stage, two-stage or variable-speed: which is worth it here?Do you need a whole-home dehumidifier on the coast?