The EU legislators have agreed that the energy efficiency first (EE1) principle is made legally binding for Member States, to apply in policy, planning and major investment decisions. Through the EE1 principle, energy efficiency is to be made a priority in European Union (EU) energy and climate policy, providing what has been a missing link in fully implementing two other guiding principles of EU energy and climate policy: costeffectiveness and consumer protection. In this article, I conduct an argumentative discourse analysis to better understand the politics of the EE1 principle in EU energy and climate policy. Two different discourses with a set of storylines were identified in the negotiations on the EE1 principle. The first focuses on multiple benefits of energy efficiency and a stronger role for the EE1 principle. The other focuses on climate change mitigation and a weaker role for the EE1 principle. The Council Presidency and the European Commission used discursive techniques such as frame polarisation, frame disconnection and frame incorporation to overcome these dualities. The description of storylines, discourse coalitions and discursive interaction strategies can help policymakers and other stakeholders become more aware of their own and others argumentation on energy efficiency and how these could be changed, thus help policymakers and stakeholders better shape their strategies in future advocacy and policymaking.