In this study, it is analysed how a large-scale implementation of plug-in hybrid electric vehicles and battery electric vehicles towards 2030 would influence the power systems of five Northern European countries, Denmark, Finland, Germany, Norway, and Sweden. Increasing shares of electric vehicles (EVs) are assumed; comprising 2.5%, 15%, 34%, and 53% of the private passenger vehicle fleet in 2015, 2020, 2025, and 2030, respectively. Results show that when charged/discharged intelligently, EVs can facilitate significantly increased wind power investments already at low vehicle fleet shares. Moreover, due to vehicle-to-grid capability, EVs can reduce the need for new coal/natural gas power capacities. Wind power can be expected to provide a large share of the electricity for EVs in several of the countries. However, if EVs are not followed up by economic support for renewable energy technologies, coal based power will in several cases, particularly in the short term, likely provide a large part of this electricity. The effects of EVs vary significantly from country to country and are sensitive to fuel and CO2 price variations. The EVs bring CO2 reductions of 1-6% in 2025 and 3-28% in 2030 while total costs are generally increased. (C) 2012 Elsevier Ltd. All rights reserved.