Hydro-electricity systems generate electricity from the flow of water. In many cases this is done on a massive scale, such as the famous Hoover Dam on the Colorado River, which when annualy generates 4.2 billion kWh. Shortly after its construction in 1936, it became the largest hydro-electric plant in the world.

There are at least 35 bigger hydro-electric plants now online or under construction, the largest being the Three Gorges Dam at 22.5 GW. Small-scale hydro systems are typically several kW (kilowatts), and are one of the most effective means of generating electricity if you have a suitable water resource.

The advantages of hydro-electricity systems are:

• Near-continual output of electricity
• Reduction or complete coverage of electricity consumption from the National Grid
• Reduction in CO² emissions through clean electricity generation
• Can be an alternative to a National Grid connection in remote areas
• Potential to sell exported electricity to the National Grid

For more information see the following websites:

• www.energysavingtrust.org.uk/Generate-your-own-energy/Hydroelectricitywww.british-hydro.org