However simple the concept is, implementing the Energy Efficiency First (EE1st) principle has proved to be a difficult task for European Union (EU) Member States. The National Energy and Climate Plans (NECPs) provide extremely limited information on how the various Member States understand and intend to implement this principle: “they set out limited details on the application of this principle [EE1st principle]”, highlighting that “co-benefits and possible trade-offs between energy efficiency measures and climate adaptation remain unrecognised and untapped” (European Commission, 2020). The European Commission is preparing guidance to aid Member States in devising their EE1st implementation strategy across various policy areas. This report provides input to this discussion. This report identifies promising policy approaches in several EU policy areas: buildings, power markets/networks, gas markets/networks, district heating, energy efficiency, climate, and EU funds. The aims are to facilitate the implementation process in Member States and guide the next steps of the project to enable more detailed analyses about barriers and success factors in implementing EE1st, and then the development of policy guidelines. We screen the policy areas and approaches by reviewing the EU policy context for each policy area; conducting interviews and using the examples of existing implementation of the EE1st principle we found earlier for each policy area. The reviews for each policy area screen the most important strategic and legislative documents where EE1st is relevant, regardless whether the principle is integrated already or not. For each policy area, we discuss a selection of policy approaches where EE1st is or could be implemented. These policy approaches have the potential to be fully implemented across the EU, bringing considerable benefits to consumers. Full and effective implementation most often requires the concerted action of various public and private actors. In each case we can identify the key actors needed for the successful Europe-wide implementation of the policy approach. In some cases, these approaches already have a legislative and regulatory basis, in others it is still to be established.