Russian aggression in Ukraine has put energy security at the top of the EU’s agenda and highlighted the need for a closer cooperation on a common energy policy. In this Policy Brief, Annika Hedberg argues that tackling the EU’s energy security challenge starts with addressing the internal challenges. A number of member states have rather naively put all their energy eggs in a Russia-basket. The EU has been slow to recognise the benefits of collaborating on energy security: national interests and bilateral energy deals continue to weaken the EU’s position vis-à-vis supplier countries. The EU’s vision for climate and energy policy, and the exact means to achieve its objectives are constantly debated. And the EU has an enormous structural and investment challenge ahead of it, if it is to move towards a more secure and sustainable energy system. The Energy Union package, adopted by the Commission on 25 February 2015, aims to build on the political momentum and boost cooperation on energy. Maintaining the momentum for action will require both sticks and carrots. The Commission must strengthen governance and enforce implementation of legislation. And the member states must be convinced of the benefits of acting together and the value of energy cooperation in the wider context of promoting security, competitiveness and sustainability.