Transitioning to a low-carbon economy requires profound changes in the energy system, including digitisation and decentralisation. Collective action energy projects are a promising means of supporting this transformation since they redistribute control of energy resources to the citizens and foster sustainable energy behaviours, as well as potentially enhancing energy justice and democracy. The EU has funded a number of collective action energy R&I projects which combine the use of new technologies and community engagement. We identify 28 such projects and investigate the types of community engagement strategies trialed and the challenges they face. We find that engagement strategies comprise a mixture of shorter term participation and longer term behaviour change strategies. There is a tendency towards behaviour change strategies based on feedback and/or rewards, while other promising strategies like targeting group norms are less common. Overall, projects opt for medium-level participation, while co-creative or more empowering approaches are less common. A lack of consistency in approach and a lack of reported data on social impacts of the projects makes it difficult to determine how effective the engagement strategies (and hence projects themselves) have been. We provide some recommendations for designing and monitoring similar research projects going forward.