What is AFUE?

This figure represents a more realistic measurement of useable heat as it applies real-life influences to the efficiency of the fireplace. Annual Fuel Utilization Efficiency is also determined by the results of some specific test conditions but these results are further calculated with other influences such as average daytime and nighttime temperatures, heat loss due to the standing pilot and from cold start up. All sorts of data is calculated to provide the overall average efficiency of the fireplace throughout the year.