ECHOES is a multi-disciplinary research project providing policy makers with comprehensive information, data, and policy-ready recommendations about the successful implementation of the Energy Union and SET plan. Individual and collective energy choices and social acceptance of energy transitions are analysed in a multi-disciplinary process including key stakeholders as co-constructors of the knowledge. To account for the rich contexts in which individuals and collectives administer their energy choices, ECHOES utilizes three complementary perspectives: 1) individual decision-making as part of collectives, 2) collectives constituting energy cultures and life-styles, and (3) formal social units such as municipalities and states. To reduce greenhouse gas emissions and create a better Energy Union, system change is required. While technological change is a key component in this change, successful implementation of that change relies on the multi-disciplinary social science knowledge that ECHOES produces. Therefore, three broad technological foci which will run as cross-cutting issues and recurrent themes through ECHOES: smart energy technologies, electric mobility, and buildings. All three technology foci address high impact areas that have been prioritised by national and international policies, and are associated with great potential savings in greenhouse gas emissions.ECHOES’ uniquely comprehensive methodological approach includes a representative multinational survey covering all 28 EU countries plus Norway and Turkey, syntheses of existing data and literature, policy assessments, as well as quantitative experiments, interviews, netnography, focus groups, workshops, site visits and case studies in eight countries. All data collected in the project will be systematised in a built-for-purpose database that will serve both as an analytical tool for the project and as a valuable resource for stakeholders and researchers after the project’s lifetime.