Due to the ambitious European and national climate protection targets, Germany is currently undergoing a restructuring of its energy system. This process is supposed to guarantee the decarbonisation of the electricity sector while taking into account the security of supply and a cost-efficient energy production. A broad decarbonisation of the energy sector combined with the phase out of nuclear energy can endanger the security of supply in Southern Germany. While most of the renewable electricity production is located in Northern Germany, a higher proportion of demand is located in the south. Therefore, the overarching goal of this research project is the analysis of the security of supply in Southern Germany in the long-term with considering interaction with other European countries, economic and climate policy related shutdowns of power stations and possible bottlenecks in the European transmission grid. The acceptance of the population, demand side management, storage technologies and the development of electricity demand, which can increase due to the propagation of Power-to-X technologies and electric mobility, are especially taken into account. For the extensive and detailed analysis of security of supply, three models developed by two different institutes are combined. Through various iterations of these models, more robust results can be identified containing capacity and grid expansions amongst others. On this basis, the security of supply in Southern Germany should be evaluated drawing policy recommendation and actions.