In this article, we analyse EU energy policy from the perspective of the EU’s long-term commitments to combat climate change. We focus on the policy integration of climate concerns – ‘climate policy integration’ (CPI). We seek to answer the question: what is the extent of CPI in energy policy, and what factors can explain this level of CPI? After outlining a conceptualisation of CPI that argues for applying a principled priority standard for the assessment of the level of integration of climate policy objectives in other policy sectors, we apply an analytical framework, with factors derived from general theories of European integration and literature on environmental policy integration, to explain the strength of CPI in two sub-energy sector case studies – renewable energy policies and internal energy market policies. CPI is found to be insufficient in both cases, and two factors are highlighted as particularly crucial for furthering CPI: political commitment to CPI, and the strong participation of climate advocates in the policy process. The article suggests that the expansion of EU competence in energy policy does not necessarily provide a guarantee for full and complete CPI.