Compressed Air Best Practices, May 2014, by Paul Johnson.
http://www.airbestpractices.com/system-assessments/piping/storage/energy-efficient-compressed-air-piping-systems

"A properly designed and maintained compressed air system that is energy efficient could save the user thousands of dollars each year. It will also minimize the risk of lost production by increasing the reliability of supply and improve the strength and safety aspect of operating a pressurized system. Every dollar saved on energy goes straight to the bottom line and is a very effective way to increase profits."