Today, distributed generation (DG) based on conventional energy sources and renewable energy sources have played a vital role throughout the world. Energy policies are promoting distributed energy resources such as energy efficiency, DG, energy storage devices, and renewable energy resources (RES), increasing the number of DG installations and especially variable output sources like wind power, solar, small hydro and combined heat and power. It can be observed that the growth rates of countries are rapidly increased. Due to environmental concern, it is very tricky to add more coal power plants for managing demand side management (DSM). To overcome from this problem, DGs are the best options for managing the need of energy. In this paper, the robustness, sustainability and reliability of DG has been discussed with various aspects and different extensive conditions. The main objective of this task is to study how to achieve a better integration of flexible demand as demand response, DSM with DGs, energy storages and Smart Grids. This would lead to an increase of the value of demand response, DSM and DG based on renewable energy sources in the substantial electricity systems and at the electricity market.