An easy way to estimate how much power you need in a heat pump is to go by the overall size of the property you want to install it in using a 600-650 square foot per ton ratio. If you live in a 2,000-square foot home, for example, you can simply divide that number by 650 for a result of 3.07, indicating that a 3-ton heat pump should be more than enough to keep your home temperate year-round. Of course, this assumes that your house is well-insulated.