Replacement of fossil fuels by hydrogen in motor vehicles throughout the world is postulated to occur over the next 50 years as mass production of fuel-cell engines accelerates. For the estimated size of the world vehicle fleet by 2050, large-scale electrolysis of water may become the primary means to produce hydrogen in sufficient quantity. Unlike petroleum production, which is concentrated in only a few well-endowed countries in the world, electrolytic production of hydrogen can be carried out in all countries as an indigenous supply of fuel. However, each nation will require a significant increase in the rate of electric energy consumption and a concomitant increase in electric power generating facilities. A dynamic model was used to estimate the annual total electric energy requirement to sustain long-term growth of hydrogen fuel production in two time sequences. In the first sequence, from 2000 to 2010, when a fuel-cell engine industry is likely to expand rapidly, extrapolation of historic data on world population, vehicle, traffic, and energy statistics from official agencies provides the initial conditions in year 2010 for the second time sequence. In the second sequence, the model examines a range of growth scenarios to the year 2050, when a significant fraction of the total world vehicle fleet could be operated with hydrogen fuel. The model calculations show that even with improved energy consumption efficiency of electrolytic production facilities, the additional electric energy demand to sustain growth of hydrogen fuel production will require installation of significant additional electric power generating capacity throughout the world,