High penetration of electric vehicles with unmanaged clustered charging will cause unwanted peaks in the electric network. It is important for the system operator to manage the impact of EV charging on the power system. This work developed a model to construct the aggregated charging load due to EVs in a parking lot while considering EV travel patterns, usage and charging needs. The EV charging load was combined with the system load to determine the reliability of the composite power system. IEEE-RTS 24 bus was used as a test system to demonstrate the efficacy of the proposed method. The DC load flow with linear programming having an objective function of minimum load curtailment was carried out to evaluate the reliability index (i.e. loss of load probability (LOLP)). The model has been validated for Shopping Center Parking Lots. Results showed that due to uncontrolled charging of EVs, the LOLP of the power system could reach up to2.3% in peak hours, whereas acceptable LOLP is < 1%. However, to maintain the reliability of the power system, it is recommended to either manage or limit the load assigned to parking lots equipped with EV chargers.