Multiple sustainability challenges are increasingly seen as demanding a fundamental transition in the energy system. In this context, community energy projects attract interest as sources for radical innovations. Studies of such bottom-up, civil society-led ‘grassroots innovations’, however, frequently highlight the profound challenges they face in growing, diffusing or even simply surviving. Strategic niche management SNM) theories are potentially useful here. They highlight the importance of ‘learning’ across different local projects, and the necessity of ‘institutionalisation’ to create a robust niche able to survive in the contemporary energy market. Crucially, this learning and institutionalisation demands dedicated work by intermediary actors. Intermediaries aggregate and share lessons from multiple projects, create networks capable of assisting future projects, and campaign for niche development, yet their work is often overlooked. Drawing on in-depth interviews and a content analysis of intermediary case studies, this paper examines the nature and extent of intermediary work in UK community energy. Analysis illuminates the difficulties faced in expanding and replicating locally-sensitive community energy projects, and tests the applicability of market-oriented innovation theories like SNM for community-based, grassroots innovations.