General Motors conducted two well-to-wheel studies for fundamental clarification on the question of which is the cleanest and most environmentally sustainable source of energy for the mobility of the future. In both studies the complete energy chains were analyzed from fuel production using primary energy to the actual consumption of the fuel in the car, i.e. from the well up to the wheels of the vehicle (well to wheel). The aim of the studies was to evaluate total energy consumption on the one hand and, on the other, the total greenhouse gas emissions arising between the production of a fuel and its final use to power an automobile. The results of the studies clearly show that fuel cell vehicles can greatly reduce greenhouse gas emissions from passenger cars or, if they run on hydrogen from renewable energy sources, they can eliminate them entirely. Regenerative fuels, however, will be more expensive than current products. With the fuel cell, because of its superior efficiency (35 - 45% less energy consumption well to wheel), it will be possible to keep individual mobility affordable in the future.