2 ton unit or smaller. if it's a modern home (modern insulation standards) and you are not an old person who likes is 76F all the time, a 2 ton would be plenty IMO.
By the cooling load of the home only.
25 cubic feet
An average 3 ton heat pump on a 1200 to 1500 sq ft home in California will typically have a 1500Watt (1.5KW) to 5000 Watt (5 KW) auxiliary heat kit installed. This is not just for emergency heat in case of compressor failure or too low of an ambient temperature to operate a heat pump efficiently, but also to temper the air going into the home while a heat pump defrosts. Since the defrost mode is the AC mode with the outside fan motor of the air going indoors will be refrigerated, this is why the heat strip wil be used to temper the air to avoid having to bring the room back up to where it was when defrost began.
it is a 12 seer 4 ton heat pump
The size of a heat pump that you can use for a pool which is 18 feet wide by 33 feet long and has a depth of 4.5 feet can vary depending on specific brand of heat pump you wish to purchase. The minimum size of heat pump for an above ground pool of this size in 102,000 BTU.
My home needs ventilation. What size attic fan would I need for a 1200 square foot house?
2.0 ton or 2.5 ton
The rule of thumb is 2-1/2 tons per 1000 square feet.
Check your owners manual for details.
2 1/2 ton heat pump, I believe 12 seer.