Background For a successful transition to a sustainable energy system, not only technical but also social innovations are required. A major challenge to social innovation research is how to translate the social innovation from a novelty with big potential into a mainstream practice. The multilevel perspective (MLP) of socio-technical transitions provides a heuristic to understand how niches can potentially break through to the regime level. In this paper, we examine in how far a multilevel perspective approach is suited to analyze and better understand diffusion trajectories of social rather than technological innovations, taking a social practice theory perspective. Five example projects, selected among the top social innovations for the Energiewende in North Rhine-Westphalia, are analyzed. We discuss to what extend the MLP provides a helpful tool to understand the transition processes. Results Social innovations can be very divers. We find that the MLP does not offer a one-size-fits-all framework for the analysis of the diffusion of social innovations. The MLP proves applicable only in those cases where the social innovation (1) can lead to a system change and (2) has a clear competing or symbiotic relationship with an existing regime. Conclusions Social innovations that aim to be transformative in the sense that they have the goal to be system changing (rather than incremental) can be analyzed along the heuristics of the MLP. For this type of social innovation, the MLP can be fruitful to learn to better understand the diffusion dynamics of social innovation and the barriers and drivers they might face. However, for social innovations that aim at incremental improvements without challenging the existing system, the MLP cannot be applied to study the diffusion process.