Since the beginning of industrialization, energy consumption has increased considerably more rapidly than the world population. In addition to the limited resources, exhaust gases resulting from the combustion of fossil fuels have adverse effects on the world climate and the health of its population. Sustainable and socially acceptable development is, therefore, only possible if more rational and technologically advanced use of conventional energy carriers is combined with an increasing contribution of renewable energy sources to the total energy consumption. Renewable energies are characterized by a diversity of resources and technologies for power ranging from a few Watts to hundreds of Megawatts. Their characteristic technologies, their potential and their present/future cost structures are described in this paper. These technologies can be adapted to any kind of energy service and are compatible with modern energy supply systems. With extended networks of centralized and decentralized power plants and heat supply systems, security of supply can be ensured. Because of the foreseeable increase in conventional energy prizes, a forceful strategy for accelerated introduction of renewable energy sources is not only a requirement for sustainable growth, but also an economically sound policy.