SEER stands for Seasonal Energy Efficiency Ratio. It measures the cooling output of an air conditioner over a typical cooling season, divided by the energy it consumes in watt-hours. In simpler terms, it tells you how efficiently an AC unit converts electricity into cooling power. A higher SEER rating signifies a more energy-efficient unit, resulting in lower energy consumption and utility bills. Modern air conditioners typically have SEER ratings ranging from 13 to 26. When replacing your AC, look for a unit with a high SEER rating to maximize energy savings over the long run.