Energy efficiency has long since been a pillar of the European internal energy policy. It now takes on increasing importance in European external energy relations. It is, for instance, key to the EU–Russian Energy Dialogue. I analyse how energy efficiency has been institutionalised in EU external energy relations, in particular towards Russia. I examine whether energy efficiency can be seen as a new paradigm for understanding external energy relations. Based on this conceptual delimitation, I describe and assess the regulatory mechanisms proposed by the EU to implement this approach in practice.