Numerous questions of great public interest can only be answered using an interdisciplinary approach within energy systems analysis. This requires a simultaneous analysis of interacting technical, economic and ecological subsystems. Systems Analysis and Technology Evaluation (IEK STE) takes on this challenge, focusing on the long-term supply and demand characteristics of energy systems. This requires above all a holistic, interdisciplinary approach that takes into account technically, economically, environmentally and socially relevant correlations. These include aspects related to the security of supply, economic efficiency and environmental protection. This three-fold strategy is oriented towards social and political principles such as sustainable development.