The heat supply in the city of Berlin will have to be substantially reformed to reach the goal of climate neutrality by 2045 while it has to cope with high gas prices today. In the research project Open Heat BE, two open numerical models are combined to analyse the short term and long term challenges of heat supply in Berlin. At TU Berlin, the energy system model GENeSYS-MOD is used at municipal scale. At DIW Berlin, the Global Gas Model is employed. Open Heat BE receives financial support by the Climate Change Center Berlin Brandenburg.