Retrofit and upgrades at existing reservoirs present significant opportunities for new energy development. In some cases, modifications are coincident with enhancements to environmental resources, recreation access, and water management. Recent national-scale assessments of technical hydropower potential suggest that approximately 4 GW of additional capacity could be added at 2,600 dams across the US. However, these estimates are derived from historical water availability and operations, and do not account for projected changes in future streamflow and reservoir storage. Our study builds on these assessments using HydroGenerate, a capacity and daily generation model, combined with streamflow projections from an ensemble of future hydroclimate scenarios. The results describe how future water availability and generation potential could shift under future hydroclimate conditions across the US. The effort identifies regions and types of facilities that exhibit the greatest differences in projected power capacity compared to estimates derived from historical conditions. This work highlights key departures from past understanding of hydropower opportunities and explores how the outlook for future water and energy infrastructure may evolve to adapt to changing conditions, benefiting infrastructure owners, policymakers, and water resource managers.