This question depends on many factors: How old is your home, thickness of walls, r-value of insulation, attic space, the amount of windows and doors in your home, and a lot of other variables! A system that is too small will run constantly, running up your energy bill. Choosing a system too large can result in a home that’s too humid which brings on moisture and mold. Only a qualified HVAC technician can calculate and determine what size unit is best for your home.