The SEER rating (Seasonal Energy Efficiency Ratio) measures an air conditioner's cooling efficiency over a typical cooling season. A higher SEER rating indicates greater energy efficiency, meaning the unit uses less energy to cool your home, resulting in lower utility bills. It is important because it helps you compare the efficiency of different models, guiding you to more cost-effective and environmentally friendly choices. Additionally, units with higher SEER ratings often qualify for rebates and incentives, providing further savings.