In recent years, renewable energies - photovoltaics and wind power in particular - have developed rapidly thanks to falling prices and are now contributing to far-reaching changes in the energy system. In order to balance out fluctuations in power production, ways must be found of aligning supply and demand. Sector coupling also makes a major contribution to broad decarbonization. These developments raise several research questions: How can the cost-efficient use of renewable energy resources be achieved in different regions? How can technologies be combined to best meet energy demands? At which points should such developments be supported by the state? We are working on answering these questions with sound techno-economic analyses.