Battery swapping mode (BSM) is an important method of supplying energy to electric vehicles, in which the battery swapping behavior of electric vehicle users affects significantly the charging behavior of the battery swapping station. To determine the impacts of a driver's swapping behavior on the power grid and generation cost, this paper proposes an optimization charging mode (OCM) and simulates the impacts of OCM on the power grid side and generation side. The empirical results indicate that the OCM significantly benefits the power grid and power generators. For the power grid side, OCM is helpful in balancing the power load and decreasing the difference of the peak and valley load. For the generation side, generators will reduce their coal consumption and cost when the OCM is conducted. In addition, OCM can integrate more renewable power into the power grid. Moreover, the empirical results demonstrate that the development of electric vehicle (EV) features scale economy. The benefits of OCM for the power grid side and generation side would be significantly improved with the increase of EV volume. (C) 2015 Elsevier Ltd. All rights reserved.