In light of the increasing reliance on renewable energy sources, Europe's energy system is facing a demand for flexibility solutions across different timeframes. A recent study by Artelys and Frontier Economics highlights the pivotal role of underground hydrogen storage (UHS) in providing this flexibility. The study emphasizes the need to enhance UHS capacity to meet the ambitious targets set by the REPowerEU plan. By 2030, 45 TWh of UHS capacity is essential, showcasing a substantial increase compared to current projections. Additionally, the study indicates that achieving over 250 TWh of UHS capacity by 2050 is imperative for the energy system's sustainability. Investing in additional UHS capacity is projected to yield a considerable economic net benefit of 2.5 billion euros annually, offering cost savings and operational efficiency. The strategic deployment of UHS enables electrolysers to operate flexibly, reducing energy system costs, greenhouse gas emissions, and renewable energy curtailment. This aligns with the goal of achieving carbon neutrality by 2050. To support the expansion of UHS, policymakers are urged to develop a dedicated hydrogen storage strategy and adopt an integrated approach to maximize synergies between different energy sectors. The study advocates for an interconnected system that leverages the potential of UHS as a versatile flexibility source, crucial for meeting the evolving energy demands. With a long lead time for UHS investments, timely intervention is crucial to unlock its benefits and ensure a competitive and climate-resilient energy economy in Europe.