Air Conditioning units are rated based on energy efficiency. This rating is called a SEER or Seasonal Energy Efficiency Rating. A SEER relates to the amount of electricity used in cooling. A SEER rating is like miles per gallon in an automobile. It is not related to a brand. That is, each SEER represents the number of BTU's of cooling per watt of electricity used. All 13 SEER rated units produce 13 BTU's of cooling per watt regardless of the brand of the unit.
Today's units have a minimum SEER rating of 13. You can also purchase units rated 14 to 23 SEER. The higher the SEER rating, the more expensive the system and the lower the operating costs. Surgi's ENERGY SAVINGS CALCULATOR will help you determine the savings of various systems to determine which efficiency rating is best for you.