Clean, reliable and secure energy supply is a key requirement for the further development of the European economy. At the same time, the Paris Agreement and its aim to limit the global warming to well below 2°C call for a quick and significant reduction of CO2 emissions, including the energy sector. In the energy sector this can only be achieved by a significant increase of the share of renewable energy sources (RES). As the most abundant RES, wind and solar, are intermittent by nature, there is a need for energy storage technologies, to provide back-up power when wind and solar output are low and more generally for load levelling and grid stabilisation. Chemical storage appears to be the most promising long-term energy storage technology. Among chemical storage technologies, hydrogen is expected to dominate as it can be produced by electrolysis of water using excess energy from RES, easily compressed and stored, and finally re-electrified using gas turbines. The goal of HYFLEXPOWER is the first-ever demonstration (at TRL7) of a fully integrated power-to-H2-to-power industrial scale installation in a real-world power plant application. The project will update and enhance an existing power plant within an industrial facility in Saillat-sur-Vienne, France. It will include the integration of energy conversion (power-to-H2) in the demonstration plant using excess energy from RES and necessary storage capabilities. The Siemens SGT-400 gas turbine will be upgraded to operate with different natural gas / H2 fuel mixtures. A key objective is the operation at full load and production of 12 MW electrical energy with high-hydrogen fuel mixtures of at least 80% by volume H2 up to 100%. The tests will also demonstrate that EU emission limits for such installations can be not only met, but also reduced. Finally, the development of an economic assessment for this Power-to-H2-to-Power pilot plant demonstration will be conducted to show the economic benefits of this application.