As the yearly electric energy demand grows, there is a significant increase in the penetration of distributed generation (DG) to fulfil this increase in demand. This book presents a methodology using Differential Evolution for the placement of DG units in electrical distribution systems to reduce power losses and to improve the voltage profile. The distributed generation (DG) sources are added to the network to mainly reduce the power losses by supplying a net amount of power. In order to minimize the line losses of power systems, it is equally important to define the size and location of local generation. There have been many studies, to define the optimal locations of DG. In this book two cases with six scenarios were considered and Differential Evolution approach was used to find the optimal locations and sizes of DG units. The suggested method was programmed under MATLAB software. The feasibility and effectiveness of the tool has been demonstrated on IEEE 33 bus radial distribution system consisting of 32 sections. Simulation results revealed that the system losses have been reduced by about 40-50 percent for the 2 Cases.The book should be useful to electrical Engineers.