On September 6th-9th, 2021 in Nottingham, UK the 17th International Symposium on District Heating and Cooling will take place. The Symposium aims at gathering the international research community around issues important for District Energy development. It is one of the most significant venues for testing research findings and learning about District Heating and Cooling. This symposium will be the 17th in the row, and expects participants from all over the world, especially from European, East Asian, and North American countries. The 17th Symposium was delayed by one year due to the Covid-19 pandemic. Now IEA DHC made the decision to organize the DHC2021 Symposium online if a face-to-face meeting is still not feasible by Mid-April 2021. There will be no further delays.