The central purpose of this paper is to introduce the reader to the basic concepts of demand side management inside smart power grids and benefits that these concepts can offer. Paper is divided into six parts described in chapters: “Influence of Renewable Energy Sources on Power System”, “Smart grid”, “Demand management in smart grids”, “Aggregator”, “Smart metering and energy box” and “Situation in Croatian Electrical Power System”. The chapter “Influence of Renewable Energy Sources on Power System” explains the influence of renewable energy sources on work process of electrical power systems, especially the bad influence of these sources on balancing and regulation of energy production and consumption. Basic structure of “smart” systems, their purpose and difficulties of implementing them is described in the chapter “Smart grid”. The next chapter – “Demand management in smart grids” offers descriptions of different types of demand side managements programs, starting from their emergence to the present day. Also, this part describes and presents results of these types of programs and also their potential in the future. Chapter “Aggregator” describes basic structure, roles and features of the „aggregation” concept. Chapter “Smart metering and energy box” describes necessary consumer’s infrastructure, its roll in demand management programs, but also implementation results of such programs. In the last chapter, named “Situation in Croatian Electrical Power System” describes the degree of use of demand respond programs in Croatian electrical power system, and also reasons why it is necessary to invest in this kind of programs.