A mobile and dispersed power system is necessary for an advanced technological-industrial society. Today's petroleum-based system discharges waste products and heat and is growing exponentially. Energy resource commitment has already intersected “ultimate” low-cost petroleum supplies in the United States and will do so for the world before 2000; this portends major changes and cost increases.The twenty-first century system for mobile-dispersed power will reflect the energy source selected to replace petroleum-for example, coal, solar insolation, or uranium. It will incorporate a fuel intermediate such as methanol, ammonia, or hydrogen, and a suitably matched “engine.”The complete change will require more than 25 years because of the magnitude, fragmentation, structural gaps, complexity, and variety of the mobile-dispersed power system. Consequently, substantial, sustained, interacting, and coordinated planning, research, and advanced development must be started now and completed during the 1970s. A “system dynamics” model of the resource-fuel engine-use complex and a “mixed economy” Energy and Ecology Cybernetics Corporation should be integral parts of the effective management of the unprecedented development of society's twenty-first century mobile-dispersed power system.