The speed and progress of transitions towards renewable energy systems varies greatly between European member states. Among others, these differences have been attributed to the emergence of grassroots initiatives (GIs) that develop radical ideas and sustainable practices. The goal of this paper is to understand the differences in the emergence of GIs for renewable energy in relation to the institutional characteristics of Denmark, the Netherlands and Sweden. We analyze the possibilities of GIs to emerge and act within three dimensions: the material-economic, the actor-institutional and discursive dimension. We conclude that conditional factors lie within the material-economic dimension in terms of the biophysical conditions, the structure of the economy, energy dependency and the energy market. Within the actor-institutional dimension, we conclude that the presence or absence of fossil fuel incumbents, such as regional utilities, strongly influence the possibilities of GIs. Within the discursive dimension, openness for alternative discourses proved to be enabling for GI-activities, as well as democratized knowledge production. In addition to these conditions of possibility, GIs can also act despite dominant institutions, albeit limited. Finally, GIs need a strong network with knowledge institutes, technology developers and political parties in order to achieve institutional change that enables GIs to flourish. Without institutional space, GIs remain subjected to the dominant power-relations, and cannot exert much influence upon the energy system