The ADEL project (ADvanced ELectrolyser for Hydrogen Production with Renewable Energy Sources) proposes to develop a new steam electrolyser concept named Intermediate Temperature Steam Electrolysis (ITSE) aiming at optimizing the electrolyser life time by decreasing its operating temperature while maintaining satisfactory performance level and high energy efficiency at the level of the complete system including the heat and power source and the electrolyser unit. The relevance of this ITSE will be assessed both at the stack level based on performance and durability tests followed by in depth post test analysis and at the system level based on flow sheets and energy efficiency calculations.