Using long-term solar and wind energy power production data series, the authors of this journal article present a modelling approach to investigate the influence of storage size and efficiency on the pathway towards a 100% renewable energy sources scenario. Applying their approach to data for Germany, the authors found that up to 50% of the overall electricity demand could be met by an optimum combination of wind and solar resources without both curtailment and storage devices if the remaining energy is provided by sufficiently flexible power plants.