Solar4Scholars: Sizes of Hydroelectric Power Plants
Some of the following information comes from the US Department of Energy's web site.
Hydroelectric facilities range in size from large power plants that supply many consumers with electricity to small and micro hydro plants that individuals operate for their own energy needs or to sell power to utilities.
Although definitions vary, DOE defines large hydropower as facilities that have a capacity of more than 30 megawatts.
Although definitions vary, DOE defines small hydropower as facilities that have a capacity of 100 kilowatts to 30 megawatts. Hydroelectric plants of this size are found in villages around the world and can contribute significantly to local economies.
A micro hydropower plant has a capacity of up to 100 kilowatts. A small or micro-hydroelectric power system can produce enough electricity for a home, farm, ranch, or village. Of all the forms of renewable energy that consumers can use independently, micro hydro is the most economical. All you need is running water on your property and permission for authorities.