Assessment of the integration of solar thermal systems in heating grids in Austria and Germany. Dynamic, long-term (up to 2050) modeling of interactions and interdepenencies of building refurbishment, decentralized heat generation and CHP with the changing power system and power prices using the heating demand model Invert/EE-Lab and the European power system simulation model HiREPS. The modells TRNSYS and SIMPLEX were used to simulate the distirct heating networks and the detailed head demand load curve. The modeling results and international case studies are used to derive conclusions about options for energy policies. Intensive involvement of stakeholders has been considered an integral part of the project.