This report provides a comprehensive global-scale assessment of the benefits, risks, and trade-offs of energy efficiency technologies and their combined effects when deployed alongside low-carbon electricity supply technologies. The results of the report show that the majority of efficiency technologies, used for mobility, buildings and industry, bring environmental co-benefits beyond greenhouse gas mitigation, including reduced impacts on the environment, health and natural resources. However, some technologies may generate higher impacts than the baseline technology for certain regions and for certain years.