To help consumers make informed choices, the U.S. Government requires efficiency rating of all air conditioning and heating equipment. The rating is meant to reflect the percentage of energy used efficiently. A high rating indicates high efficiency. There are various names for efficiency ratings depending on the equipment.
Air conditioners are rated by Seasonal Energy Efficient Rating (SEER). Heat pump equipment is rated by the Heating Seasonal Performance Factor (HSPF). Gas furnaces are rated in accordance to their Annual Fuel Utilization Efficiency (AFUE).