In high-, 40 to 60% of process energy goes to melting metal. The remainder is used for the actual . The energy input needed for melting depends on the amount of scrap (typically 5 to 7%), melting losses (2 to 5%), and casting yield, the ratio between casting weight and total pouring weight (30 to 70%).
Raw metal is usually melted with natural gas, but the amount needed can vary by a factor of seven, depending on the equipment and environmental policies of different foundries. And the amount of electricity used can vary by a factor of two, for an average value of 5,603 kW-hr per metric ton of final castings. With these uncertainties, simulation can help designers better design and place gating systems, which can significantly reduce the amount of energy needed.