In the HVAC world you need to size equipment properly. If you oversize it on the cool side, you can create an environment that is damp, wet. The system will not

In the HVAC world you need to size equipment properly. If you oversize it on the cool side, you can create an environment that is damp, wet. The system will not run long enough to remove the humidity from the the environment and cool it to quickly. It causes a cool humid environment. Now that same system that is oversized will need to heat your house in the Winter. It becomes inefficient because it is too large for the environment it is trying to heat. AC units aren't sized just for heat, they are sized for the sq/ft of the house and the zone they are in, that determines their size. Furnaces are sized in the same way (size of house and zone it is in), so if you live in Florida and you need a heat pump that is perhaps 4-5 ton, the Heat side of it will be perhaps 70 % larger than it needs to because you could get away with perhaps a 1-1.5 ton Heat Pump in the Winter months since it isn't cold. So you need 5 tons in the Summer and 1-1.5 tons in the Winter. It's like using a dump truck for your job and then using it as your personal transportation also.