The Seasonal Energy Efficiency Ratio measures how efficient your air conditioner was throughout a standard cooling season. The higher the SEER rating, the more energy efficient your cooling system is. Equipment that earns a high-enough SEER rating is eligible for ENERGY-STAR distinction, which means it meets federal guidelines for energy efficiency. The minimum will change depending on your local climate region. Many modern air conditioners can boast SEER ratings as high as 25.