This course provides theory and hands-on experience about energy system modelling for buildings and cities. Lectures cover physical concepts, mathematical laws, and software tools for city and building energy system modelling. This course starts with heat transfer basics and building thermal dynamics. Then it teaches energy system modelling using Modelica, an emerging equation-based programming language. Both the building-scale energy system (HVAC) and the city-scale energy system (district heating and cooling system) are covered. Through hands-on tutorials, students learn Modelica (with IDE of Dymola) and use it to simulate energy systems for buildings and cities. Instructor’s approval is required.