This paper outlines a method of determining energy losses in power system elements (transmission lines, transformers, etc.) The method is based on knowing typical daily load curves (DLC) of different kinds of load. The idea of the proposed method is to use statistical mathematics to organize the entire data that is in the load curves in order to provide only a few quantities needed to calculate energy losses. These quantities, called statistical moments, include all the useful information about the DLC. The method gives accurate results compared with direct computation and is several times faster than any other existing simulation or direct technique. © 1989 IEEE