The predominant strategy to reduce CO2 emissions in the transport sector is its renewable based electrification. It implies mobile storages that could - during long phases of immobility - provide services for the electricity sector. However, this technical option - called vehicle-to-grid (V2G) - requires the vehicle users to temporarily abstain from the usage of their batteries for V2G. A reasonable estimate of the potential of V2G thus considers which individual, technical and economic parameters are decisive for the willingness of vehicle users to participate. To answer these questions a representative sample of vehicle users in Germany has been surveyed - including a discrete choice experiment. 'Range anxiety' and the 'minimum range' proved most important determinants of the willingness of vehicle users to participate in V2G. If these concerns are smoothed out, even without remuneration, high participation rates might be achieved. To increase the participation in the V2G technology, the transition from 'tank control' to 'mobility demand articulation' should be facilitated for vehicle users. Therefore, companies could tailor the V2G design to customers' needs and policy could improve information about V2G. Remuneration, however, cannot be expected to be very supportive.