To support the current trend of testing bigger reversible Solid Oxide Cell (rSOC) modules, CEA has built the 120 kW DC Multistack platform. It was used to test SOLIDpower recently developed-Large Stack Module (LSM) in electrolysis mode. Results show high thermal performance of the LSM, with homogeneous temperature distribution and losses in the kilowatt range above 700 °C. A performance map was recorded between 712 and 744 °C over 22.4-to-29.6 kg h−1 steam flowrates using a fast control strategy to avoid endothermic operation. A peak power of 74 kW DC was converted into more than 50 kg day−1 of H 2 (35.5 kWh DC kgH 2 −1). In addition, fuel utilization of more than 90% and steam conversion above 80% were demonstrated at the module level. In the end, the modular design of the LSM seems well suited for system scale up, paving the way for mutualization of auxiliaries and CAPEX reduction. • CEA has built the Multistack platform to test rSOC modules of up to 120 kW DC. • SOLIDpower has developed the Large Stack Module integrating four G8X stack towers. • A peak power of 74 kW DC was converted into more than 50 kg day−1 of H 2. • Excellent thermal performances were recorded with losses in the kW range above 700 °C. [ABSTRACT FROM AUTHOR]