The overarching aim of SONNET is to develop a systematic understanding of the ways and conditions under which social innovation in the energy sector can contribute to the Energy Union Strategy and enable a clean energy transition of Europe’s energy system. To achieve this aim SONNET will explore the links between citizen involvement, social innovation and transformative changes within the energy system in order to develop evidence to examine its central hypothesis: social innovation in the energy sector induces new forms of social interactions, governance arrangements and business models, which enable greater civic engagement and empowerment as well as social acceptance to drive the clean-energy transition, making energy more secure, sustainable and affordable. The empirical focus will be on social innovation in urban areas located within low-carbon regions and carbon-intensive regions.