The focus of this paper is the need to achieve energy efficient work regimes in the operation of actual pump systems, because of the impact which energy efficiency has on the utilization of electricity by a system. Some of the main factors influencing the efficiency of a system’s crucial elements also have been examined. A quick and easy method for a quantitative assessment of a pump system’s efficiency also has been presented. The reliability of this methodology has been tested and confirmed. In conclusion, a method for the theoretical determining of the effective work regimes for a centrifugal pump with a trimmed impeller has been given.