In this study, different effects of EVs (electric vehicles)/PHEVs (plug-in hybrid electric vehicles) with V2G (vehicle-to-grid) connection capability and renewable energy sources used as DGs (distributed generators) on a power distribution network are analyzed. A power distribution network including CPGs (conventional power generators) located in powerhouses, different types of renewable energy sources consisting of PV (photovoltaic), WT (wind turbine) and FC (fuel cell) systems used as DGs, and EVs with V2G connection capability is considered. Limitations of the power distribution network and an objective function including the power production cost, power loss, and voltage profile that are the most significant parameters of a power grid are defined. The objective function is minimized in the four cases that are the grid with CPGs, the grid with CPGs and DGs, the grid with CPGs and EVs, and the grid with CPGs, DGs and EVs. For the first time, theoretical results together with simulation verifications performed in ETAP/MATLAB environments explicitly verify that the lowest electric power production cost and the best voltage profile are obtained by simultaneously utilizing CPGs, renewable energy sources used as DGs and charging/discharging EVs, while the lowest power loss is obtained by utilizing CPGs and DGs in a grid. (C) 2015 Elsevier Ltd. All rights reserved.