Hydropower or hydroelectricity refers to the conversion of energy from flowing water into electricity. It is considered a renewable energy source because the water cycle is constantly renewed by the sun. Historically, one of the first uses of hydropower was for mechanical millings, such as grinding grains.

The primary use of hydropower energy is to produce electricity. The main ingredients of hydroelectric power plants are dams, rivers, and turbines. Hydropower is the most advanced and mature renewable energy technology and provides some level of electricity generation in more than 160 countries worldwide. Hydro is a renewable energy source and has the advantages of low greenhouse gas emissions, low operating costs, and a high ramp rate (quick response to electricity demand), enabling it to be used for either base or peak load electricity generation, or both.