Climate change, added to security of supply concerns, has been leading many countries to strongly support the development of electric vehicles (EVs) not only as a cleaner and more energy efficient source of trans. Climate change, added to security of supply concerns, has been leading policy makers to p. In order to investigate the impact of EVs on power system operation and its costs, a mid-term operation model that simulates power system operation during one year with daily period. The Spanish power system represents an interesting case study for this analysis due to the significant penetration of intermittent generation in that country. Strong support for renewable ge. 4.1. Power system operation4.2. System operation costsIn order to better understand the impact of EVs on total system operation costs, first, it is important to an. This paper analyzed the impact of the integration of EVs with V2G capability on power system operation costs considering different EVs and RES generation penetration level.