This study, commissioned by the Swiss Federal Office of Energy (SFOE), analyzes the future development of security of supply in the electricity sector in Switzerland. Following on from the System Adequacy (SA) studies of 2017 and 2019, a three-stage model chain is used to investigate the long-term adequacy of generation and network capacity in Switzerland and Europe up to 2040. The current SA study sets a focus on the role of import capacity for the Swiss supply situation – especially during the winter – as well as medium- to long-term developments of different renewable energy pathways.