This project presents a method based on GAMS software, which aim is to determine the optimal size of a microgrid connected to the grid, and the influence of electrical vehicles (EV) in the developing of the investment decision. The technologies considered in the study are wind turbines, solar panels (PV), batteries, EV and the microgrid can have the possibility to be connected to the grid or not. A sensitivity analysis will be performed in order to check the influence of the weather and of the technologies taken in to account. Finally, an analysis of the optimal scheduling of the system will be presented. Results show that for this type of system batteries aren’t available in any scenario, while electrical vehicles used as batteries can have a very important role for the energy transition. Furthermore it is highlighted the importance to consider as many technologies as possible in order to low total costs of the system. The simulation is a mixed integer nonlinear programming performed with the solver IPOPT.