Interoperability depends on cooperation of multiple domains. While for the energy sector technical interoperability is quite well established, interoperability of functions and businesses needs more attention. Even when standards are defined and interoperability models agreed, framework setters, product developers and users need to agree on their deployment and make sure that solutions are compatible with definitions. The Interoperability Network for the Energy Transition project (IntNET) establishes an open, cross-domain community bringing together all stakeholders relevant for the European energy sector to jointly work on developing, testing and deploying interoperable energy services. The community will be formally established to exist beyond project life-time. With a comprehensive, FAIR knowledge platform and a series of attractive events it guides those who deal with the heterogeneous interoperability landscape of energy services. To support ongoing harmonization of energy services, IntNET will institutionalise an assessment methodology and maturity model (IMM). Involving legal and regulatory bodies from the beginning and constant exchange of interoperability initiatives and standardization bodies will build a deep consensus on how European governance and industry can foster interoperability at all levels. Starting from an extraordinary well balanced and connected consortium of researchers, framework setters (e.g., ministry and EU wide associations), standardisation and communication experts, IntNET’s community approach guarantees wide outreach. IntNET will establish a framework for interoperability testing in ongoing projects and harmonize test procedures in a network of closely cooperating, self-sustained testing facilities. Energy service solutions based on the novel IMM and tested according to the IntNET certification process will be awarded with a widely known quality seal for interoperable smart grid and energy products (working title: “IntNET approved").