A total of 29 U.S. states and the District of Columbia have in place mandatory Renewable Portfolio Standards (RPS) which require that a minimum amount of energy come from renewable resources. We investigate the role of hydropower vis-a-vis other renewables under RPS. Using a Bayesian multilevel model, we find that hydropower plants subject to RPS are more likely to plan upgrades. These planned upgrades appear to be a substitute for solar and wind rather than complementary reserve generation.