The shift to a low-carbon EU economy raises the challenge of integrating renewable energy (RES) and cutting the CO2 emissions of energy intensive industries (EII). In this context, hydrogen produced from RES will contribute to decarbonize those industries, as feedstock/fuel/energy storage. MULTIPLHY thus aims to install, integrate and operate the world’s first high-temperature electrolyser (HTE) system in multi-megawatt-scale (~2.4 MW), in a renewable products refinery in Rotterdam, the Netherlands, to produce green hydrogen for the refinery’s processes. MULTIPLHY offers the unique opportunity to demonstrate the technological and industrial leadership of the EU in Solid Oxide Electrolyser Cell (SOEC) technology. With its rated electrical connection of ~3.5 MWel,AC,BOL, electrical rated nominal power of ~2.6 MWel,AC and a hydrogen production rate ≥ 670 Nm³/h, this HTE will cover ~40 % of the current average hydrogen demand of the chemical refinery. This leads to GHG emission reductions of ~8,000 tonnes during the planned minimum HTE operation time (16,000 h). MULTIPLHY’s electrical efficiency (85 %el,LHV) will be at least 20 % higher than efficiencies of low temperature electrolysers, enabling the cutting of operational costs and the reduction of the connected load at the refinery and hence the impact on the local power grid. A multidisciplinary consortium gathers NESTE (a Green Refiner as end-user), ENGIE (a global energy system integrator & operator), PaulWurth (Engineering Procurement Construction company for hydrogen processing units), Sunfire (HTE technology provider) and the world-class RTO CEA. They focus on operation under realistic conditions and market frameworks to enable the commercialisation of the HTE technology. By demonstrating reliable system operation with a proven availability of ≥ 98 %, complemented by a benchmark study for stacks in the 10 kW range, critical questions regarding durability, robustness, degradation as well as service and maintenance are addressed