PROSEU aims to enable the mainstreaming of the prosumer phenomenon into the European Energy Union. Prosumers are active energy users who both consume and produce renewable energy (RE). The growth of prosumerism all over Europe challenges current energy market structures and institutions. PROSEU research will look into new business models, market regulations, infrastructural integration, technology scenarios and energy policies. PROSEU’s interdisciplinary and transdisciplinary team will closely work together with RE Prosumer Initiatives (15 Living Labs), policymakers and other stakeholders from eight countries, following a quasi-experimental approach to learn how prosumer communities, start-ups and businesses are dealing with their own challenges, and to determine what incentive structures will enable the mainstreaming of RE Prosumerism, while safeguarding citizen participation, inclusiveness and transparency. Moving beyond a case by case and fragmented body of research on prosumers, PROSEU will build an integrated knowledge framework for a socio-political, socioeconomic, business and financial, technological, socio-technical and sociocultural understanding of RE prosumerism and coalesce in a comprehensive identification and assessment of incentive structures to enable the process of mainstreaming RE prosumers in the context of the energy transition.