This article positions collective renewable energy prosumerism as a social movement that engages in energy system transformation. Collective renewable energy prosumer initiatives engage in ‘prefigurative’ work through their discursive framings (ways of thinking), their activities (ways of doing) and their understanding and enactment of social relations (ways of organising). The core of this article is a comparative analysis of the prefigurative work of 13 collective prosumers from 7 European countries (Belgium, Croatia, Germany, Italy, Netherlands, Portugal, United Kingdom). The article discusses their contributions to energy system transformation, including renewable energy production, different mechanisms for involving citizens, local value creation, and the degree of desired and actual collaboration and networking within broader prosumer ecosystems. We then discuss these contributions against societal discourses and expectations towards prosumerism, such as energy democracy, energy justice, and environmental sustainability and decarbonisation. This reveals three tensions: 1) a focus on decarbonisation but not on broader environmental problems, 2) the involvement of certain people and not of others, and 3) the building of prosumer eco-systems while ignoring incumbency. Future research avenues are formulated to conclude the article.