Recently, the penetration of distributed generations (DG) has been obviously increased in electric distribution networks throughout the world. DGs are small scale generators connected near load centers in networks, thereby avoiding losses in transmission systems and releasing system capacity. At present, there are many types of DG, such as wind power, solar power, fuel cell, biomass, micro-turbines, and diesel engines. DG can play an important role in improving the performance of the networks; therefore, allocating DG optimally is one of the most crucial subjects in DG planning. In this chapter, the DG allocation problem is studied, and an efficient method is presented for accurately solving this optimization problem. The proposed method combines between analytical expressions and an optimal power flow (OPF) algorithm to determine the optimal locations, sizes and the best mix of various DG types for minimizing the total real power loss in electric distribution networks. The proposed analytical expressions are general for directly calculating the optimal sizes of any combination of multi-type DG technologies. The optimal power factors of the various units can be analytically computed, thereby contributing positively to loss reduction. The 69-bus test system is used to test the proposed method. The effectiveness of the proposed method is demonstrated for determining the optimal mix of various combinations of different DG types.