At the most basic level, "energy transition" can be understood as a fundamental change to the pre-existing state of the energy system. Usually it is expected that these changes concern large trends taking place at the international or global level, and that the changes are long lasting and also shape the societies in question. This relatively simple notion of energy transitions is not the only possible option. Theoretically driven transition studies refer to "transitions" to entail "far reaching changes to sectors of economy in which new technologies, institutional structures and organizations emerge and existing ones change or decline. Such transitions are referred to as socio-technical transitions". 1 Socio-technical systems which are fundamentally transformed can be viewed as a "network of actors (organizations but also individuals) and institutions, such as societal and technical norms, standards, regulations or user practices as well as material artefacts and knowledge". 2 Today, the energy world is going through a number of fundamental transitions. The most commonly discussed and examined transition is the transition towards a more sustainable energy system. 3 For energy transitions researchers who focus on this area of transition studies, "Sustainability transitions are long-term transformational process of established industries, socio-technical systems and societies to more sustainable modes of production and consumption." 4 Sustainability transitions or sustainable development can be defined as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs". 5 It has a strong environmental aspect built into it ("environmental sustainability" 6 ) but it also has an economic and social aspect to it. Also the 1992 Rio Declaration includes these elements: "States should cooperate to promote a supportive and open international economic system that would lead to economic growth and sustainable development in all countries, to better address the problems of environmental degradation". 7 In practice, combining these environmental, social and economic aspects of 1