In this article, we analyze the role of social capital in the formation of sustainable energy communities. Specifically, we study the impact of different dimensions of social capital (i.e., structural, relational, cognitive) in determining willingness to participate in an energy community. Our survey data suggest that social contexts contribute to the development of energy communities, via (at least) two channels: (i) a family path, with individual perspectives showing a partial correlation with those of at least one relative, and (ii) a social channel, with higher social trust and greater interaction with neighbors favoring the propensity to participate in an energy community. The social coordination required for the formation of sustainable energy communities is determined by the quality of social interactions, and the spread of virtuous behavior is determined by not only economic policies (i.e., incentives), but also forward-looking policies favoring local aggregation and the creation of high-quality social capital. Thus, local actions and interactions can contribute to solving global climate change challenges.