The transition to sustainable energy sources introduces distributed intermittent energy that requires more flexibility in demand. It is anticipated that consumers will play an active role with self-generation and will pro-actively manage their demand according to their needs and available resources; this is called Demand Side Flexibility (DSF). Energy Management applications will be used to control consumption, generation and storage, so that consumers will be in control, but will not need to execute all the related actions themselves. These applications will take input from Smart Meters and signals from energy market players to control the in-home energy flows. To that end, the data needed for DSF needs to flow seamlessly through an IT infrastructure that connects Smart Meters, Consumer Energy Management Systems, Smart Appliances and Gateways between the home and external networks. The IT infrastructure of DSF is covered by three different industries that all have separately developed technology and standards, i.e., the Utility industry, the Telecom industry and the Home appliances industry. Originated for different purposes and in different context, the communication standards from these industries are not necessarily aligned, leading to barriers in the seamless flow of data in the DSF infrastructure. In this study, we have investigated the need for alignment among the communication standards from the Utility, Telecom and Home appliances industries. We have selected nine standards that have been compared with the reference ontology SAREF (Smart Appliances REFerence ontology), developed in an earlier project commissioned by DG-Connect, and its extension for the Energy domain, SAREF4ENER. We concluded that alignment between DSF standards is needed and that SAREF/SAREF4ENER can be used as the overarching ontology to facilitate this alignment. Several actions and recommendations for various stakeholders, such as the Standards Development Organisations, have been identified and are listed in the report. Moreover, a proof of concept was demonstrated to show DSF interoperability through the complete, end-to-end IT infrastructure, from Smart Grid to Smart Meters and Smart Appliances. The next step to be taken is to scale up the proof of concept that we demonstrated, implementing the resulting SAREF-based solution in more use cases for Demand Side Flexibility, in more smart devices and at real consumer sites.