The energy intensity of primary aluminum production has been reduced significantly over the last 20 years due to improvements made in the magnetic design of electrical conductor bus components, application of state-of-the-art computer systems for control and management of cell operations, use of alumina point feeder systems, and chemistry changes. Large, modern cells operate with a specific energy consumption of 5.9 to 6.4 kWh/lb of aluminum. The energy required to produce aluminum from scrap metal is approximately 5% of that required for primary production. [DOE 1997] The charts below, which give additional measures for aluminum production energy intensity, illustrate decreasing energy intensity over time.