<p>In the available literature, the optimal power and allocation of distributed energy source (DES) or parallel compensation system (PCS) in the power grid is usually determined by using some optimization algorithms. In that goal, the application of metaheuristic algorithms is dominant. Although the application of these algorithms has a few advantages, its main disadvantage is the principle of operation based on the rand() function. This paper presents a novel approach for only a single optimal allocation and sizing of a distributive generator or a parallel compensation device in a radial distribution network. The criteria function is the minimization of total active power losses in a system. The proposed approach takes into account the radial configuration of the network as well as the value of bus voltages and power factors in the case without adding DES/PSC in the network. It is tested on the IEEE 33, 69, and 85-bus test systems. The comparison of the proposed approach with other approaches presented in the identified literature in terms of total active power losses, optimal bus location, optimal DES/PCS size, bus voltages as well as in the number of calculations and elapsed time is also realized. The proposed approach reaches the desired optimum very quickly compared to literature approaches with the same or better accuracy. All results confirm the superiority of the proposed approach and represent it as an understanding, very powerful, and innovative approach for a single optimal DES/PCS device allocation and sizing problem.</p>