Improvements in energy efficiency and reductions in energy demand are expected to contribute more than half of the reduction in global carbon emissions over the next few decades. These unprecedented reductions require transformations in the systems that provide energy services. However, the dominant analytical perspectives, grounded in neoclassical economics and social psychology, focus upon marginal changes and provide only limited guidance on how such transformations may occur and how they can be shaped. We argue that a socio-technical transitions perspective is more suited to address the complexity of the challenges involved. This perspective understands energy services as being provided through large-scale, capital intensive and long-lived infrastructures that co-evolve with technologies, institutions, skills, knowledge and behaviours to create broader ‘sociotechnical systems’. To provide guidance for research in this area, this paper identifies and describes thirteen debates in socio-technical transitions research, organized under the headings of emergence, diffusion and impact, as well as more synthetic cross-cutting issues.