Substantial Global Pumped Hydroelectric Storage Resource Persists Under Environmental Constraints

Long-duration energy storage is essential for stabilizing electricity systems dominated by wind and solar power1, yet the global potential of pumped hydroelectric storage (PHS) under realistic hydrological, environmental, and social constraints is unresolved. Here we present a global, bottom-up assessment of PHS by integrating river discharge, long-term precipitation–evaporation balance, topography, protected landscapes, land-use exclusions, population displacement thresholds, and infrastructure accessibility. Screening 2.89 million river and 50 million mountain valleys, we identify a total of 19.03 ± 2.67 PWh of economically and environmentally viable PHS resources. This resource is strongly concentrated in high-elevation terrain across Asia and the Americas, while low-relief and water-limited regions exhibit significant intrinsic constraints. Under projected electricity demand conditions (2050), the identified PHS can provide more than 100 hours of storage duration for 58.4% of global electricity consumption. Although PHS remains the most cost-effective option for long-duration energy storage beyond three hours, its large-scale deployment is fundamentally constrained by geography, hydrology, environmental suitability, and transmission accessibility. These constraints define a hard physical boundary on the role of PHS in future power systems and underscore the necessity of integrating complementary storage technologies to achieve resilient, low-carbon electricity systems.