Energy nation


Status: Renewable

What is it?

Indirect solar power drives the Earth's water cycle. Energy from the Sun evaporates water from seas and lakes. This water falls as rain. Some ends up in lakes and reservoirs, high above sea level. This water has gravitational potential energy, which is transformed into kinetic energy as it flows down towards the sea.

How is it used to generate electricity?

The kinetic energy of flowing water spins a turbine which is connected to a generator which creates electricity.

Where can you find it?

Hydroelectric power stations need to be near large lakes, reservoirs high above sea level or where a large flow of water can be dammed.

Advantages and disadvantages of using hydroelectric energy to generate electricity


  • Once the plant is built, operating costs are very low so the energy produced is virtually free
  • It does not produce any carbon dioxide, which can lead to global warming, making countries hotter and drier
  • It is sustainable – the rain that fills the reservoir never runs out
  • Dams store water so we can control when electricity is made
  • Power output can be increased very quickly to meet sudden demand
  • Electricity can be generated constantly as long as there is enough water


  • Dams are very expensive to build
  • Valuable land is flooded when a reservoir is made: homes and wildlife habitats can be lost
  • A good site for a hydroelectric power plant, such as a mountainous region, is not always near towns where energy is needed
  • There are not many suitable sites in the UK for new hydroelectric schemes

How many power schemes in the UK?

7 (50MW schemes). 

The future?

It is unlikely that there will be a huge increase in hydroelectric power in the UK as all large-scale sites are being used, but some small-scale sites are being developed.