The main goal of the BALANCE proposal is to gather leading research centres in Europe in the domain of Solid Oxide Electrolysis (SOE) and Solid Oxide Fuel Cells (SOFC) to collaborate and accelerate the development of European Reversible Solid Oxide Cell (ReSOC) technology. ReSOC is an electrochemical device that converts electrical energy into hydrogen (electrolysis mode) or alternatively fuel gas to electrical energy (fuel cell mode). It is characterised by its very high efficiency compared to competing technologies. ReSOC enables to store renewable electricity when it is produced in excess or to convert it into a CO2-free transport fuel. Therefore, it is considered as a key technology to allow the broad penetration of renewable electricity into the European energy system.Fragmented national research efforts are currently impeding quicker development and deployment of next-generation fuel cell and hydrogen technologies. Therefore, BALANCE will identify, quantify and analyse national activities dealing with the diverse aspects of ReSOC technology. This analysis will result in an integrated European research agenda for ReSOC technology to gain synergies and to generate breakthroughs in this highly promising but currently low-TRL technology. Close communication with the advisory board will enable alignment of the proposed agenda with the roadmaps and activities of EERA, IEC and IEA on the topic of hydrogen technologies.Technical development will cover the development of the next generation of ReSOC cells, their integration in the optimised stack assembly, and investigation of the constraints from reversible operation at system level and integration with the grid. Cost will be addressed by using low-cost materials and improving manufacturability. The experimental work will be supported by modelling and simulation at all scales and by the techno-economic analysis of different integration of the ReSOC technology in industrial applications.