Hydrogen cars are electric cars whose energy is carried by pressurized hydrogen. The technology is in its infancy, especially on the manufacture of fuel cells at reasonable cost. Right now, hydrogen is made from natural gas, and the only gain, at great expense, is barely a doubling of the efficiency of burning the gas directly in reciprocating engine. Carbon dioxide is still emitted in the generation of hydrogen. Hydrogen is clean energy only when fission or fusion plants supply the energy to hydrolyze water to make it. Other nonpolluting sources such as hydroelectricity and solar and wind farms are not sufficient to replace the 383 million gallons of gasoline we consume per day in the USA [29]. The infrastructure for distributing hydrogen [4] will cost perhaps half a trillion dollars.