The acronym AFUE stands for Annual Fuel Utilization Efficiency. It is a thermal rating granted to furnaces based on their efficiency. Basically, it measures the amount of energy drawn from the fuel source against the amount of hot air produced. The higher the rating, the higher the energy efficiency. Most new furnaces are rated at 80% or greater, and they can go up to 98%. This aspect of the furnace is increasingly important to consumers looking for cost-effectiveness and “green” efficiency, but AFUE rating is only one factor. More importantly, the overall efficiency of your heating system depends upon the quality of the installation and integrity of your ductwork.