As part of its climate and energy package, Germany has set ambitious long-term goals to reduce greenhouse gas emissions 80 percent, primary energy consumption 50 percent, and power consumption 25 percent by 2050. Meeting these goals will require aggressive investment in end-use energy efficiency. Consequently, policymakers will need a keen understanding of efficiency as a power system resource and a strong grasp of its costs and benefits. This study explores the electric system benefits of deep investment in energy efficiency in Germany. It examines five development paths for the German electricity system from 2012 through 2050. The authors examine how different levels of electric end-use efficiency result in different levels of electricity demand, and in turn, how the different levels of demand impact the magnitude, composition, and cost of not only electricity production, but also the reinforcement and expansion of the transmission and distribution grid. As described in the study, the increased levels of efficiency yield significant reductions in the total costs of generation—both conventional and renewable—and of the transmission and distribution infrastructure. The study was jointly commissioned by RAP, Agora Energiewende, and the European Climate Foundation.