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What is hydropower?

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Hydropower is the renewable energy contained in flowing water. Electricity generated using hydropower is known as hydroelectricity and is generally considered to be reliable.

In the UK there are three main methods for generating hydroelectricity:

  • storage – where a dam collects water in a reservoir, then releases it to drive turbines, producing electricity
  • pumped storage – where water is pumped to a higher reservoir, usually during times of low-priced electricity, then released to a lower reservoir, again driving a turbine, usually when the electricity price is higher
  • run-of-river – where the natural flow of a river or stream is used to drive a turbine.


The cost-effectiveness of a hydroelectric power station is affected by the geography of the site it is built on.

The disadvantage of hydropower is that most suitable sites in the UK are already home to hydroelectric power stations, so there is very little scope to increase hydroelectricity's small (about 1.4%) share of the UK's electricity generation mix in the future.

Information sources

How electricity is generated through hydropower

Infographic illiutrates how electicity is generated through hydropower

See how hydroelectricity is generated at a dam.

Is it plentiful?

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As a renewable energy source, hydropower is theoretically inexhaustible, but the best sites have already been exploited.

Is it secure?

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As an indigenous energy source hydro is highly secure, but the number of sites where large-scale hydro can be sited in the UK is limited, so it will only ever make a small contribution to the energy mix.

Is it predictable?

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UK hydropower stations have an assumed availability at peak of 60%. Hydro might be a minor player in terms of total UK generating capacity, but its inherent reliability contributes to the overall reliability of the electricity supply.

Is it affordable?

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It is currently not considered economically viable to build new large-scale hydropower stations in the UK. The affordability challenges facing hydropower are minimal and well-established but possible new sites in the UK are limited. 

Is it clean?

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Hydropower stations have a carbon footprint of around 10–30gCO2e/kWh. Hydroelectric dams require significant quantities of carbon-intense concrete but their long life spreads this over years of near zero-carbon electricity generation.

EDF Energy's approach

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Hydropower is not part of EDF Energy's mix of generating technologies in the UK.