E4tech reviewed and summarised current water electrolysis technology and the potential for cost reduction and performance improvement to 2030. We consulted stakeholders throughout the electrolyser value chain. Together with our project partner Element Energy, we modelled specific hydrogen production cost for different end-use cases to identify which technology developments had the most influence on the commercial viability of the technology. The analysis included indirect value streams, such as grid balancing services and avoided grid reinforcement, and specific examples of national electricity markets, such as exemptions from electricity levies. We outlined a roadmap for electrolyser development and deployment that could make water electrolysis a key part of the future energy system. The FCHJU Program Office is using the results of our study to inform their funding priorities.