Electrical power system is one of the most complex and advanced systems in the world. The energy management of such a system from the point of generation and distribution has been optimized but the demand side has only received attention in the last decade. This has led to the implementation of demand side management (DSM) which involves a number of different methods to improve the power system at the demand side. DSM ranges from increasing load efficiency by using better materials to implementing smart energy tariffs for different consumption patterns, up to using sophisticated systems to control distributed energy sources. This paper gives an overview of the DSM and discusses in detail the different ways of implementing the DSM in the electrical power system.