Low-carbon district heating in Sweden – Examining a successful energy transition

District heating (DH) systems may contribute to reducing the use of fossil fuels for heating purposes since they enable the use of waste heat and facilitate the use of renewable energy sources. This paper focuses on the transformation of the Swedish DH systems with regard to energy supply in 1960–2011. Swedish DH production was completely dependent on oil until the late 1970s, while today it is dominated by biomass and other renewable energy sources. The objectives of this paper are to describe and explain the fuel transition in the context of the main events that have characterized the development of the Swedish DH sector. For this purpose, we employ theories and approaches grounded in the literature on systems of innovations, especially the Multi-Level Perspective. The study shows that the transition involved a series of steps. Initiated by the oil crises in the 1970s the oil-based regime collapsed rapidly, while the growth of the biomass-based regime was a steered process governed by actors and supported only by external events. The lessons learned from the transition towards low-carbon and more sustainable DH systems in Sweden could be useful in the challenging task of steering future energy transitions in other countries and sectors.