The aims of this paper are to: 1. Show, based on concrete examples of national and local policies, initiatives and projects, how energy efficiency can be a key driver for market transformation and to demonstrate its social, economic and environmental benefits through clear indicators of success; and 2. Position UNEP as a key player in the field of energy efficiency. The report i) Summarises why energy efficiency and behavioural change are important and what they can be expected to contribute to the mitigation of climate change and a transition to a green economy and reviews some important aspects of initiatives that will bear on future technical cooperation in energy efficiency that will condition the context for UNEP’s future work; ii) Sets out some of the key aspects of public policy intervention in energy efficiency. It analyses why intervention is justified and what instruments have been used to influence productive activities and consumer behaviour and how they have generally performed; iii) Recapitulates some of the past achievements of UNEP that are relevant to energy efficiency and present some selected case studies of activities that may be suitable for a long-term programme; iv) Reviews the lessons of practice in energy efficiency as demonstrated by projects of UNEP, other international agencies and national governments; and v) Examines options for the future positioning of UNEP’s work, taking into account its past experience of energy efficiency, its general mission and capabilities, the development of the field as a whole and the competences of other players.