What is hydroelectric energy and how does it work?

Find out how electricity is generated from flowing water.

- 

If you’ve ever seen a river rushing down a mountain or played in breaking waves at the beach, you’ll know that moving water contains a lot of energy. A river can push you and your kayak downstream, sometimes very quickly, and waves crashing into you at the beach can knock you back, or even knock you over.

Energy in flowing water

The energy in these moving waters comes from gravity. Water travels around Earth in a water cycle (see below). Water evaporates (turns into a gas) from the surface or is released from plants (transpiration). When the released water vapour is carried up to higher altitudes – such as mountainous regions – it cools down and condenses into liquid cloud droplets. When these cloud droplets become big enough, they fall from the sky as precipitation, either as a liquid rain or – if it is cold enough – as a solid snow.