When it comes to the proper size of your central air conditioner, your home will dictate what it should be. Square footage, insulation, window type, and ceiling height are all factors that impact the size you need to efficiently cool your home. Once you consult with an expert on the appropriate size of your central air conditioning unit, you need to consider the SEER (Seasonal Energy Efficiency Rating). SEER is a number that charts the efficiency of your central air conditioning unit. The higher the SEER rating, the more energy efficient the central air conditioning unit will be, and the lower your monthly energy bills. Importantly, however, a higher or lower SEER will not cool your home any better. It simply uses less energy to reach your desired temperature.