In general terms there are only three primary energy sources: fossil fuels, renewable energy, and nuclear fission. For fueling road transportation, there has been much speculation about the use of hydrogen as an energy carrier, which would usher in the “hydrogen economy.” A parallel situation would use a simple battery to store electricity directly in order to power vehicles. The efficiency of these two different approaches has been compared and shows that the hydrogen and fuel cell system would consume nearly (...) three times the primary energy required by a battery storage system. Successful introduction into the marketplace of the plug-in hybrid vehicle would eliminate the need for road vehicles to use petroleum fuels, at least for the majority of miles traveled. If electricity were to be generated primarily from sustainable primary energy sources, then road transportation would also become sustainable, resulting in an “electricity economy” rather than a “hydrogen economy.”. (shrink)