This part of ISO 13579 specifies a general methodology for measuring energy balance and calculating the efficiency of the process involving reheating furnaces for steel as designed by furnace manufacturers. This general methodology includes:

This part of ISO 13579 is not applicable to any efficiencies related to the process itself outside of reheating furnaces for steel (e.g. in a rolling mill process, the reheating furnace is the only part covered by this part of ISO 13579).