In recent years, power generation based on renewable energy has been penetrated in the power system. However, intermittency of renewable energy has resulted in several problems such as system frequency fluctuation. In order to suppress the system frequency fluctuation, a battery inside an electric vehicle (EV) is expected to be used as a control device for Load Frequency Control (LFC). Nevertheless, the driving behavior of EV users is uncertainty therefore the control may want to consider parameters which affect the system’s performance. This paper focuses on sensitivity analysis of step smart charging scheme. The total controllable capacity of the EVs is estimated based on the lumped EV model. The result shows that change of input parameters affect the effectiveness of the system’s performance.