Although other renewable energy sources such as solar and wind are gaining wide adoption, hydroelectricity maintains its position as the cheapest source of electricity globally.
In terms of production costs, hydropower holds a strong advantage over solar power. The U.S. Department of Energy calls hydropower the most common and least expensive form of renewable energy in the United States. Hydroelectricity represents 6 percent of all U.S. energy production and accounts for 70 percent of all renewable energy generated in the United States.
There is a great difference between the hydropower and the solar power. The hydro power is intensive while solar power is of low density. While the hydropower stations require classical materials and machines to erect, the pv stations require advanced technologies and electronic materials. So, the cost comparison will be in favor of the hydropower.
At this moment hydro power is cheaper than solar power . This is due to cost of conversion of the solar energy. Silicone cells are rather costly . However, solar energy is sustainable source of energy. If in future if the solar energy conversion cells are made with cheaper cost , then solar energy can become cheaper than hydro-power as per my opinion.
Hydropower is the least expensive source of renewable energy in the United States, including solar power (see References 2). Hydropower creates greater environmental impacts than solar energy,