There is a general agreement that the history of the development of human societies is a history of the complex transition from one energy production system to another. However, the political issue of the energy transition emerged overwhelmingly after the 1970s energy-environmental crises, along with the critical reflections on the sustainability of the development model. In the last two decades, the sustainable energy transition also became one of the main issues of international climate change policies. This issue is part of political agendas that propose strategies to decouple economic growth from the degradation of nature. Concepts like ‘sustainable development’, ‘green economy’, ‘circular economy’ and, recently, the ‘green new deal’, despite their ambivalent definition, have offered discursive schemes to define transition policies. At the same time, social scientists have increasingly analysed the contradictions and complexities of the turn to a sustainable energy society. By reporting some of the main theoretical reflections on energy transition, we aim to highlight the socio-political complexity and contradictions of this process. Also, in the Conclusions a brief description of energy policies is provided, highlighting assumptions and trends of the ongoing green transformation.