The Use of Energy System Models for Analysing the Transition to Low-Carbon Cities – The Case of Oslo Arne Lind 1 , Kari Espegren 1 1 Institute for Energy Technology (IFE) P.O. Box 40, NO-2027 Kjeller, Norway Phone (+47) 92281635, Fax (+47) 63812905 E-mail: arne.lind@ife.no Abstract More than half of the world’s population are living in cities today, and by 2050 almost 75% of the population will live in urban areas. Thus, meeting the energy demand in urban areas in a sustainable way is an important challenge for the future. Oslo wants to show how cities can take leadership in the green change and contribute with innovative ideas and solutions for development of sustainable energy systems. A technology-rich optimisation model has been developed in order to analyse how various energy and climate measures can transform Oslo into a low-carbon city. Consequently, the main focus of this work has been to find optimal ways of reducing the CO2 emissions, and secondly, the energy consumption. Keywords: Urban energy system; energy system model; scenario analysis; renewable energy; CO2 emissions 1. Introduction In 2014, 54 per cent of the world’s population were living in urban areas [1]. Globally, urbanisation is taking place rapidly, especially in less economically