There is a growing awareness among academics and policy makers that the energy transition is linked to the active participation of stakeholders in their different roles as users, producers, consumers or owners. Stakeholders should therefore not only be seen in a passive role, but more broadly as empowered actors in the energy transition. The dimensions of citizen co-creation include their role in co-designing policies and legislation, co-producing solutions and innovations, co-implementing projects and, finally, being co-beneficiaries of the green transition process. This approach is embodied in the EU’s new strategy to make clean energy a reality for all Europeans. In the Horizon Europe project, called “Hybrid services from advanced thermal energy storage systems (HYSTORE)”, we use a co-creation methodology to involve people who interact with the demonstration sites where the pilot energy storage systems will be implemented. People with different skills, technical and non-technical, and different roles—decision-makers, professionals, workers, residents, business people, representatives of social enterprises and cooperatives, housing associations, consumer organisations—are involved in the process of defining the characteristics of the new technology and identifying the motivations that could lead people to accept and use it. In our contribution to the conference, we would like to present the method and procedures used to implement co-creation activities in the development of a new technology, highlight some key aspects to consider in the planning phase.