A stereotypical understanding of EU-Russia energy relations is often reduced to trade in oil and natural gas, which downplays the importance of energy efficiency cooperation. Such cooperation is promoted within the Energy Charter and its Treaty, Partnership and Cooperation Agreement, Energy Dialogue, Common Economic Space, Partnership for Modernisation. However, it lacks practical development, which relates to the instability of the legal environment in Russia, insufficient mechanisms of financial support for energy conservation projects and poor political support. Nevertheless, energy efficiency cooperation is capable of changing Russia-EU energy cooperation qualitatively: it offers a cheaper way to meet the needs of the EU, redefines interdependence between the parties, and introduces new elements of equality between them. Energy efficiency cooperation also transforms the patterns of the EU-Russia legal harmonization, creates new conditions for the convergence of regulations and the development of the middle class in Russia. Due to its specific features, cooperation in the Baltic Sea region becomes a locomotive of the Russia-EU energy efficiency cooperation, and, as a result, is capable of changing the quality of relations between the partners.