The power system operators are looking for optimizing the power generating resources in the unit commitment problems considering the binding constraints. With the reconstruction in the power network structure, the increase in electricity price during some hours of day, and increase in fuel price, the utilities need to change their management paradigms. A smart grid can be a suitable choice for addressing these issues because they are able to continue working smartly. With the progress in the technology of batteries, power electronic devices, many well-known companies such as Toyota and Tesla have started producing electric and hybrid vehicles since 1990. Introducing electric vehicles to the power system provides unprecedented environmental and economic opportunities and at the same time new challenges to deal with for the system operators. The vehicle to grid (V2G) technology can enable the electric vehicles to inject energy to the grid in addition to its regular path of receiving energy from the grid. In this paper, the effect of the technology of V2G on the operation cost and LMP with considering the line congestion limits are investigated. To solve the optimization problem, a mixed integer linear programming (MILP) technique in the GAMS software is used. The proposed method is tested on the IEEE 6 bus system and the results are presented. This simulation shows that although the presence of electric vehicles has no significant effect on reducing or increasing of the operation cost in smart grid and may even reduce the operation cost in a certain number of EVs, due to their daily trips and shift from a bus to another bus, they act as a transmission line during the day and reduce the line congestion, resulting in a significant reduction in the local marginal price (LMP) in the peak load hours, and also increasing the security of the power system when the line capacity falls.