Abstract: A method for improving the energy efficiency of a pump system. The method includes measuring an instantaneous power consumption of the pump system, measuring an instantaneous fluid flow rate of the pump system, and determining an instantaneous specific energy consumption (SEC) of the pump system based on the instantaneous power consumption and the instantaneous fluid flow rate. The method then adjusts the speed of a pump in response to the determined SEC. The above steps may be performed a number of times to seek a reduced value of the instantaneous SEC of the pump system.