This report examines the potential impacts of data sharing related to electric vehicle battery charging and electricity provision. The report arrives at a moment of regulatory ambiguity in the EU over the nature of data sharing that will be involved in this industry and whether there will be EU rules or national rules that ensure choice and prevent data monopolisation. Resolving the ambiguity is important due to the potentially decisive role that car batteries can ultimately play in storing variable renewable energy, like wind and solar, and returning this energy to the network at times of high demand. We maintain that the main regulatory challenges are represented by the policy choices related to interoperability and standardisation, in particular the option for a mandated rather than a facilitated API adoption, and the concerns about privacy and cybersecurity. Failure to require openness at an early stage is not likely to be counteracted by high customer demand for openness and could create lock-in for car customers to “mini” monopolies. Openness does not require imposition of one standard: openness only implies open access to each standard and information hel