Visions of and narratives about the future energy system influence the actual creation of innovations and are thus accompanying the current energy transition. Particularly in times of change and uncertainty, visions gain crucial relevance: imagining possible futures impacts the current social reality by both creating certain spaces of action and shaping technical artifacts. However, different actors may express divergent visions of the future energy system and its implementation. Looking at a particular innovation site involving multiple stakeholders over an 8-year period, (...) we empirically analyze the collective negotiation process of vision making, its shifting over time, and how visions eventually unfold performativity. Adopting a process perspective, we identify four different phases and the respective functions of visions and visioneering related to the site’s development by exploring the question: Why do certain visions gain importance and eventually lead to substantial changes of the project in process? Qualitative data from documents and interviews analyzed with reference to science and technology studies show the interweaving conditions that influence the visioneering and the linkage to the actual development of material artifacts. Against the backdrop of innovation projects, this paper explores visioneering as an ongoing, transformative and collective process and reveals its moments of stabilization. (shrink)