Choosing the right size for a new air conditioner
A larger unit is not a better one. The Department of Energy says correct sizing matters most in humid climates, where short-cycling can lead to poor humidity control, and that extra starts and stops accelerate wear and tear on the equipment. The same fact sheet cautions against sizing from floor area or contractor experience alone and points to the Manual J load calculation and Manual S equipment selection from the Air Conditioning Contractors of America. DOE: Right-size heating and cooling equipment.
Before we name a model, we measure what the cooling has to work against: the walls, ceilings and windows, which way the house faces, and the ducts that will carry the air. Your proposal states the capacity we picked and the reason.