In this paper the authors discuss a case history of improving the energy efficiency of a water system's pumping operations by means of in-place pump testing to determine individual pump performance, field testing of pressure- regulating valve settings, and simulating system behavior over a 24-hour period with an extended-period computer model of the system. The model showed that an energy cost savings of 9 percent could be achieved with existing pumping equipment and that improvements to the pumping system could result in a 20 percent savings. Includes tables, figures.