TEASER is an open-source urban energy modelling tool to enable the use of building performance simulations for large building stocks developed by RWTH Aachen University, E.ON Energy Research Center, Institute of Energy Efficient Buildings and Indoor Climate. TEASER provides a methodology to create full-scale building data sets for single and up to thousands of buildings. Therefore the tool uses archetype buildings with minimal input requirements (building function, net leased area, year of construction and rough cubature) and data enrichment. TEASER holds classes and functions for data acquisition, data enrichment, data manipulation, model parameterization and Modelica code generation. Currently two Reduced Order Models from two different Modelica libraries are supported (AixLib, https://github.com/RWTH-EBC/AixLib and Annex60 https://github.com/iea-annex60/modelica-annex60). We provide archetype functionalities for the German building stock. However, TEASER is open to integrate other archetype methodologies. Further highlights are CityGML support and easy-to-use retrofit options to estimate energy demands. Although in this state of the development we recommend the use of a script-based interface to TEASER, the release includes a GUI in beta phase. TEASER is pure Python and freely available under the MIT license. We welcome you to take part in the development of TEASER by cloning it from GitHub.