The Modelica library TransiEnt is being developed within the research project TransiEnt.EE. After completion, the library will be freely available and will provide a framework to model coupled energy supply grids, i.e. electricity, district heating, and gas grids, including their corresponding producers, consumers and storage systems. This paper presents the current status of the library and outlines the library’s structure and the modeling concept. The application possibilities of the library are presented in an exemplary simulation where the city of Hamburg is selected as the reference system. The impact of a high share of fluctuating renewable energy generation in the electric grid and the integration of excess electricity in the district heating network is presented.