The increasing integration of renewables in the electrical power system requires the provision of large amount of flexibility to guarantee a secure and optimal operation of the European grid. Hydropower plants already provide critical grid support and ancillary services, namely: fast regulation and frequency control, fast start and stop times and ramping rates, fast transition from pump mode to generating mode, and fault ride through capability. The EU-funded XFLEX project aims to enhance the hydropower potential and its capability to provide flexibility services to the grid. To achieve this objective, XFLEX will demonstrate an innovative methodology for system integration of hydroelectric technology solutions, and analyse their impact on the modern power market. These innovative solutions will also optimise maintenance intervals, decrease outage times and increase the availability of the entire European hydroelectric power plant fleet.