Hydroelectricity represented the largest share of electricity generation among renewable sources in 19 states in 2017, according to the U.S. Energy Information Administration. By comparison, hydro was the largest renewable electricity source in 28 states in 2007. EIA says the drop in 2017 correlates with wind and solar becoming more common. Wind was the most prevalent renewable electricity generation source in 16 states in 2017 and solar was the most prevalent in seven states.
Source: Hydro Review