Hydroelectric plants have advantages compared to other energy sources. The water cycle (evaporation, clouds, rain) is a natural process, driven by the sun. Therefore the water supply to hydroelectric plants is renewed and practically inexhaustible.
In addition a hydroelectric plant produces no heat or other contamination to the environment. The use of hydroelectric plants varies from country to country because of differences  on rainfall,  mountains and rivers.

Hydroelectric factories does not cause serious environmental problems, though the following can be mentioned:
- The river stops at the dam. Beyond that point there is no river. Some types of fish that swim to the sources of the river to multiply can not do that
- In order to operate the hydroelectric plant an artificial lake is built. That means an area that before was a cultivated area now is covered with water.