Rating numbers indicate the efficiency of heating and air conditioning equipment and are directly related to the amount of energy a specific model uses. The higher the rating, the more efficient the product, and the lower your heating and cooling bills can be. The federal government establishes rating guidelines and sets minimum efficiency levels. For cooling, the rating is SEER (Seasonal Energy Efficiency Ratio). For heat pumps, the rating is HSPF (Heating Seasonal Performance Factor). Gas furnaces are rated with AFUE (Annual Fuel Utilization Efficiency).