The table compares the energy and performance densities of different energy sources. In case of fossil fuels it has to be taken into account that the weight of the tank reduces the listed values by approx. 15 %. The fuel cell, strictly speaking, is not an energy source, but rather an energy converter. Since electrical energy is produced, it is generally considered as an alternative to conventional sources of electrical energy. The actual energy source is hydrogen which has to be carried along.
It becomes clear that fossil fuels exceed by far, all alternatives in the context of their energy density, except for pure hydrogen. Even in their highest stage of development, electrical energy sources show unacceptable conditions concerning their employment in motor vehicles, predominantly as a result of their difficult operating behavior. Only the fuel cell presently offers an essential development potential.