Pumped hydro energy storage, traditionally reliant on large reservoirs and elevation, is undergoing a renaissance via technological advances such as dense mineral-based fluids that reduce spatial and elevation requirements. Demonstration projects in the UK show potential for vastly expanded site viability. Large-scale deployments like the 3.6 GW Fengning plant and the under-construction 350 GWh Snowy 2.0 project underscore the method's capacity for massive energy buffering integral to balancing variable renewable sources. Challenges remain, including lengthy construction timelines, high costs, and environmental compliance, exemplified by delays and fines at Snowy 2.0. Nevertheless, pumped hydro's rapid response capability and scalability position it as a cornerstone for decarbonized grids, complementing intermittent wind and solar power as global renewable penetration grows.