During the last few years’ electric vehicles started to catch more attention. According to environmental policies of major states and unions of states, the number of electric vehicles will be increasing in the next years. In this thesis is studied the problem of unit commitment with high penetration of renewable sources, by presenting different methods for forecasting the renewable production. Furthermore, a model of a flexible load from electric vehicles is integrated into the unit commitment models. The aim of this research is to study the impact of the excessive load on the production side and compare different unit commitment models. It is demonstrated that optimized charging is cheaper than random charging for all the models and allows higher numbers of electric vehicles to be integrated into the electric system. Simulations showed that the cost of energy increased slightly by 1% for the optimized charging profile when using 100% electric vehicles penetration, whereas in the random charging profile the increase was around 15% for the same percentage of electric vehicles penetration.