This study explores the future cost and performance of water electrolysis technologies, specifically Alkaline Electrolysis Cells (AEC), Proton Exchange Membrane Electrolysis Cells (PEMEC), and Solid Oxide Electrolysis Cells (SOEC), through expert elicitation. The research aims to support decision-making in the face of limited data and uncertainty. Key findings include: 1. **Technology Dominance**: Most experts predict a shift from AEC to PEMEC by 2030, driven by the latter's superior characteristics for intermittent operation and flexible manufacturing methods. SOEC is also expected to gain traction, particularly in co-electrolysis or fuel cell applications. 2. **Capital Costs**: By 2020, PEMEC is estimated to have significantly lower capital costs compared to AEC, with a reduction of 0–24% through increased R&D funding and 17–30% through production scale-up. SOEC is projected to have the highest capital costs, but potential cost reductions through production scale-up are significant. 3. **System Lifetimes**: Experts estimate that AEC and PEMEC lifetimes will converge around 60,000–90,000 hours by 2020 and 2030, with SOEC showing the most significant improvement in lifetime. 4. **Efficiency and Environmental Impact**: Experts highlight that efficiency improvements are less prioritized due to low operating costs and the focus on reducing capital costs. However, innovations in catalysts, electrodes, and membranes are expected to enhance efficiency. Environmental impact is considered minor, with carbon dioxide emissions being insignificant compared to other hydrogen production technologies. 5. **Innovations and Recommendations**: Key innovations include improved manufacturing methods, automation, and system designs. The study recommends policies that encourage investments in production methods and product standardization to automate manufacturing and produce higher-quality components. Research should focus on SOEC systems and novel AEC and PEMEC system designs. Overall, the study demonstrates the value of expert elicitation in guiding near-term investment, policy, and research efforts to support the development of electrolysis for low-carbon energy systems.This study explores the future cost and performance of water electrolysis technologies, specifically Alkaline Electrolysis Cells (AEC), Proton Exchange Membrane Electrolysis Cells (PEMEC), and Solid Oxide Electrolysis Cells (SOEC), through expert elicitation. The research aims to support decision-making in the face of limited data and uncertainty. Key findings include: 1. **Technology Dominance**: Most experts predict a shift from AEC to PEMEC by 2030, driven by the latter's superior characteristics for intermittent operation and flexible manufacturing methods. SOEC is also expected to gain traction, particularly in co-electrolysis or fuel cell applications. 2. **Capital Costs**: By 2020, PEMEC is estimated to have significantly lower capital costs compared to AEC, with a reduction of 0–24% through increased R&D funding and 17–30% through production scale-up. SOEC is projected to have the highest capital costs, but potential cost reductions through production scale-up are significant. 3. **System Lifetimes**: Experts estimate that AEC and PEMEC lifetimes will converge around 60,000–90,000 hours by 2020 and 2030, with SOEC showing the most significant improvement in lifetime. 4. **Efficiency and Environmental Impact**: Experts highlight that efficiency improvements are less prioritized due to low operating costs and the focus on reducing capital costs. However, innovations in catalysts, electrodes, and membranes are expected to enhance efficiency. Environmental impact is considered minor, with carbon dioxide emissions being insignificant compared to other hydrogen production technologies. 5. **Innovations and Recommendations**: Key innovations include improved manufacturing methods, automation, and system designs. The study recommends policies that encourage investments in production methods and product standardization to automate manufacturing and produce higher-quality components. Research should focus on SOEC systems and novel AEC and PEMEC system designs. Overall, the study demonstrates the value of expert elicitation in guiding near-term investment, policy, and research efforts to support the development of electrolysis for low-carbon energy systems.