This paper explores how power relations are manifested, altered and/or reproduced in processes of social innovations in energy transitions (SIE). We explore this research question by developing an interdisciplinary and transdisciplinary power heuristic building on different dimensions of power: power to, power over and power with. This conceptual framework helps us analyse the power dynamics in multiple types of SIEs that aim to contribute to sustainable energy transitions across three different national contexts: Germany, Poland, and the United Kingdom (UK). Our findings show how social innovation involves different dimensions of power to/over/with, and how power relations are both altered and reproduced. The cases under study also lead us to argue that understanding how power dynamics develop requires the analysis of the interplay between different power dimensions across the multiplicity of actors within different SIE-fields and their initiatives.