The work is devoted to solving the problem of optimizing the flow of reactive energy in electric grids (EG) of electric supply companies (EC). The object of research is the process of transportation and distribution of electric power by electric grids of UES. The subject of the research is methods and means for optimizing the flow of reactive energy in such grids. One of the most problematic locations for the EG operation is ensuring their energy efficiency in the face of constant changes in consumption and generation of electricity. It is known that the most effective measure to reduce power losses in the EG is the introduction of measures to optimize the flow of reactive energy. However, in order to optimize the location of additional reactive power sources (RPS), it is necessary to solve the problems of non-linear multifactor optimization, which is associated with a number of problems. On the basis of the research it is shown that to optimize the RPS location it is expedient to use the results of modeling «ideal» EG modes for reactive power based on equivalent circuits with active supports. The economic costs associated with the installation and operation of the RPS, it is suggested to list the EG equivalent circuit in the corresponding economic supports. Mathematical relations for economic resistance of established RPSs are developed, as well as the optimization task to be determined based on the results of the solution. Application of this approach, unlike classical methods, significantly shortens the calculation time and allows obtaining a solution close to the global minimum of production costs. The computational efficiency and reliability of the approach is ensured by the construction of the task of multifactorial optimization of the flow of reactive energy in the design setting in the iterative calculation of the «ideal» EG mode according to the appropriate equivalent circuit and loads. The program implementation allows to confirm the effectiveness of the proposed approach for a number of practical problems. It is shown that the solutions obtained for optimizing the RPS distribution in grids bring the profitability of investments to a global maximum closer, regardless of the size of the problem and a list of constraints on the parameters.