The fostered implementation of volatile renewable energy sources will trigger a raising demand of grid ancillary services in the upcoming years. However, future electrified road vehicles provide significant energy storage capacities, since they are unused for most of the time. In this regard, this study analyses for various electric vehicle (EV) use cases the potential for providing grid ancillary services based on the vehicle-to-grid technology. Therefore, we estimate the future demand of ancillary services in 2030 in terms of redispatch measures and control reserve. Real-life EV mobility patterns demonstrate, that EVs are perfectly suitable for the provision of ancillary services, even with low discharging power. Assuming a sufficient EV-penetration, private EVs charging at home or at work may cover a substantial share of required grid ancillary services. Besides EV users' mobility patterns, long-term load flow simulations illustrate the limitation of possible grid ancillary services due to local grid restrictions, especially with high discharging and charging power. Consequently, an increase of charging and discharging power only slightly raises the actual share of provided grid ancillary services compared to a low-power bidirectional power exchange between grid and EV.