Actors play a key role in promoting or hindering sustainability transitions and their positions and the coalitions they form may adjust during this long-term process. Literature widely recognizes the importance of coalitions to create legitimacy and build support for sustainability transitions. The question of how coalitions change in the third, acceleration phase of a transition has, however, remained insufficiently explored. This paper analyses advocacy coalitions in the acceleration phase of the European energy transition and sheds light on the dynamics between niche and regime level actors when the transition is already well underway. Whereas earlier studies identified one renewable energy coalition, we find three distinct coalitions in the EU's electricity policy system that support the transition but with preferences for different policy instruments. Our study shows that rather than coalition decline and growth, the ongoing development involves the emergence of new coalitions and new alliances between them.