High temperature steam electrolysis (HTSE) is one of the most promising ways for hydrogen mass production. If coupled to a CO2-free electricity and a low cost heat source, this process is liable to a high efficiency. High levels of performance and durability, in association with cost-effective stack and system components are the key points. To reach such goals, a low-weight stack has been designed, keeping the advantages of the high performing and robust stack previously validated in terms of performance, durability, and cyclability [1], but aiming at reducing the cost by the use of thin interconnects. This low-weight stack has demonstrated at the scale of a 3-cell stack a good performance of -1.0 A cm-2 at 1.3 V at 800 °C. Before performing the durability test, preliminary studies at the cell level have been carried out to highlight the effect of two major operating parameters that are the current density and the steam conversion (SC) ratio, those studies being carried out at one temperature, 800 °C. Based on these results, optimized operating parameters have been defined to perform the durability test on the stack, that is -0.5 A cm-2 and a SC ratio of 25%. Degradation rates around 3-4% 1,000 h-1 have been measured. The thermal cyclability of this stack has also been demonstrated with one thermal cycle. Therefore it can be concluded that these results make HTSE technology getting closer to the objectives of performance, durability, thermal cyclability, and cost.< Réduire