In industrialized countries such as Germany, electricity production contributes 30-40% of the greenhouse gas (GHG) emissions of the country. Confronted with GHG emission reductions targets of 80-95% by 2050 and with some GHG emitting sectors confronted with great difficulties to reach such targets, such as agriculture, the power sector will need to reduce its GHG emissions virtually to zero. As nuclear energy involves very substantial accident risks and the unsolved problem of safe long-term deposit of nuclear waste and as carbon dioxide capture and storage (CCS) has rather limited safe storage potentials at least in Europe, the question arises, whether it will be possible to supply 100% of all necessary electricity from renewable energy sources? We show that a fast expanding volume of analyses underlines the feasibility and reliability of 100% renewable electricity supply systems. This fast mounting evidence appears to mark the beginning of a paradigm shift in energy politics, as highly regarded national and international advisory bodies such as the IPCC or the German Council of Environmental Advisors start to adopt this perspective. The example of the highly publicized study of the German Council of Environmental Advisors shows how a 100% renewable electricity system for Germany, Europe, and North Africa could look in 2050 and how the transition toward such a system could be achieved. This study, conducted with major input from the authors, is used to show the major aspects of a 100% renewable electricity supply system, such as the security of supply in every hour of the year, the compensation of intermittent sources such as wind and solar PV energy by other renewables and expanded storage, and the necessary extension of national and international grid infrastructures.