By the cooling load of the home only.
A 4 ton heat pump should be fine, depends on how well your house is insulated. If the house is well insulated you might be fine with a smaller unit.
25 cubic feet
The average cost to recharge a home heat pump can vary depending on the size and type of heat pump, the refrigerant needed, and local labor rates. On average, it can cost between $300 to $1000 to recharge a home heat pump. It is recommended to consult with a professional HVAC technician for an accurate estimate.
4-5 tons
2 ton
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.
it is a 12 seer 4 ton heat pump
2.0 ton or 2.5 ton
The rule of thumb is 2-1/2 tons per 1000 square feet.
You cannot accurately determine what size furnace is required based on the total square feet of a given space or structure. To accurately determine how much heat is required to heat your, you would need to have a Manual J Heat Load Calculation performed.
Check your owners manual for details.