In this paper we investigate the impact of different electric vehicle charging strategies on spot market power prices for the case of Germany. We also provide a detailed analysis of uncertainties resulting from vehicle-to-grid (V2G), the most flexible charging option. Since the integration of renewable energy sources requires flexibility, we compare V2G with two competing systemic flexibility options provided by highly flexible power plants and resulting from EU high voltage grid expansion, respectively. In all cases we find that V2G has by far the most significant impact on prices, mainly smoothing them, while reducing, for example, the surplus electricity from renewable energy sources. V2G also has the strongest influence on prices compared to the systemic flexibility options of more flexible power plants or network expansion. In addition, we show that it is important to take the structural difference between working days and weekends into account. Especially on weekend days, which are usually characterized by low power demand, V2G raises power prices the most. Finally, the price effects are accompanied by a saturation effect, which is already noticeable in the German case at two million vehicles. (C) 2018 Elsevier Ltd. All rights reserved.