The Seasonal Energy Efficiency Ratio (SEER) measures how efficiently an air conditioning system cools a given space and the amount of electricity needed to do so. The higher the SEER rating, the more energy-efficient the system is. The minimum SEER rating for air conditioners sold in the United States is 13, while ENERGY STAR qualified central air conditioners must have a SEER of at least 14. The minimum SEER rating for federal tax credit is 16, which applies to split systems where the condenser and compressor are housed separately. However, the definition of a good SEER rating varies depending on the homeowners individual preferences. Some homeowners prioritize air conditioner efficiency, in which case a SEER rating of 17 or higher would be ideal. Others may prioritize unit affordability, which would make a SEER rating of 14 or 15 more ideal.

In summary, the minimum SEER rating for air conditioners sold in the United States is 13, while ENERGY STAR qualified central air conditioners must have a SEER of at least 14. A good SEER rating is typically 14 or higher, but the definition of a good SEER rating varies depending on the homeowners individual preferences.