This book addresses the rapidly changing citizen roles in innovation, technology adoption, intermediation, market creation and legitimacy building for low-carbon solutions. It links research in innovation studies, sustainability transitions and science & technology studies and builds a new approach for the study of user contributions to innovation and sociotechnical change. Citizen Activities in Energy Transition gives detailed and empirically grounded overall appraisal of citizens’ active technological engagement in the current energy transition, in an era when Internet connectivity has given rise to important new forms of citizen communities and interactions. It elaborates a new way to study users in sociotechnical change through long-term ethnographic and historical research and reports its deployment in a major, decade-long line of investigation on user activities in small-scale renewables, addressing user contributions from the early years to the late proliferation stages of small-scale renewable energy technologies (S-RETs). It offers an empirical and theoretical understanding of the dynamics of the activities in which users are engaged in the course of sociotechnical change, including innovation, adoption, adjustment, intermediation, community building, digital communities, market creation, and legitimacy creation.