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Electric vehicles (EVs) can form a massive energy storage system (referred as Vehicle-to-grid, V2G) in electrical power system, charging during low demand times and discharging when power is in need and prices are high, with consequences of reduced peak load, system reliability improvement, CO2 emission reduction and economic benefits. Regulators, policy analysts, utility companies and EV owners have been debating the merits of using EVs as mass energy storages in power system operation. At the core of this debate is the cost and benefits of EV batteries in V2G application. The paper analyses three types of EV batteries: lead-acid, lithium-ion and NiMH, which have been the top three contending technologies for EV batteries due to a combination of performance capability, safety, life and cost. Simulation studies were carried out based on applications in China. Numerical results show that ambient temperature plays a crucial role in the cost of battery wear; consequently the cost of EV participating in V2G in summer is much greater than that in any other season. An increase in ambient temperature results in reduced EV battery cycle life. Results also show that given current vehicle battery costs and current utility electricity tariff structure in China, no EV would be cost-effective as peak power resources. However, lithium-ion based EVs have the greatest potential for V2G due to its long lifetime and lower sensitivity to ambient temperature. The results presented in this paper can be a reference for the policy maker to stipulate incentives encouraging EVs to participate in V2G application.