The current agenda in the field of environmental policies and climate change highlights the rational use of energy and the adoption of conservation mechanisms, brought together in guidelines for energy efficiency and sustainable development. In this context, the Brazilian National Energy Efficiency Plan, inspired by national energy conservation programmes, puts into practice measures of the National Energy Plan 2030. The Brazilian National Energy Efficiency Plan demonstrates the potential of efficiency measures in various sectors, such as industry, transportation, buildings, lighting, in long-term planning, and from an integrated perspective of available resources. This chapter will analyse the adequacy of legal and political mechanisms to promote energy efficiency in Brazil, based on the State’s duty to develop instruments that ensure the efficient allocation of energy resources and environmental preservation. In a context of severe environmental crisis and probable energy crisis, the need for the use of renewable energy sources arises, taking into account the dependence on Brazilian hydroelectric generation, and the high cost of thermoelectric energy production as a possible source in the face of the water crisis. It is necessary to re-signify the right to energy efficiency in Brazil, both through legislative updating (the main legal framework on the subject is from 2001 – Law No. 10.295/2001), and through the practical manifestation of effective public policies that directly involve society in its concretisation, in a perspective of public governance.