Hydropower in the UK continues to expand and develop into a vital renewable energy source.

Although hydropower currently ranks fourth amongst renewable energy sources, behind wind, biomass, and solar, it is a growing area of development with many new sites receiving investment.

Within the hydropower sector, there is still significant untapped potential. As the UK approaches its 2030 Clean Power goals, hydropower will become an increasingly important part of the renewable energy mix.

What is hydropower?

Hydropower is a sustainable, renewable energy source that uses the flow of water to generate electricity. It is one of the oldest forms of renewable energy, with the first hydropower generator in the UK dating back to 1878.

Despite a fivefold increase in hydropower plants since 2003, the sector has not expanded as rapidly as wind or solar. This slower growth can be attributed to the key drawbacks of hydropower, such as the need for substantial land to build, high upfront costs, and the extensive planning and permitting processes required.

Types of hydropower

Hydropower is an umbrella term for several technologies that use the flow of water to generate electricity. The following types are currently in use across the UK, each with their own advantages and limitations:

Impoundment plants – This system uses a dam and a reservoir to control the flow of water. Electricity is generated when water is released from the dam and passes through a turbine.

Diversion plants (run-of-river) – This system is placed within a portion of a canal, river or tunnel and is connected to a generator. The natural flow of water is then used to turn the turbine and generate electricity.

Pumped-storage plants – This system works based on two reservoirs at different levels. Its purpose is to act as a large-scale battery storage plant. During periods of low electricity demand, water is pumped between the upper and lower reservoirs with the energy stored and then provided to National Grid when needed.

Offshore hydropower plants – Tidal and wave energy plants are located offshore, where they harness the energy of ocean waves, tides, and currents to generate electricity. While the immense power of the ocean allows for greater energy generation, these plants are significantly more difficult to install and maintain, making them less common than onshore hydropower plants.

Although the specific advantages and disadvantages of each type of hydropower plant vary, together they offer a sustainable source of renewable energy that tend to operate regardless of weather conditions and time of the day.

What is the state of hydropower in the UK?

As it stands, there are over 1,600 hydropower plants in the UK, with 2GWs of installed electricity capacity. Although the number of plants has increased significantly over the past 20 years, hydropower in the UK only accounts for 2.2% of renewable energy sources.

According to the British Hydropower Association, hydropower in the UK is usually relied upon when other renewable sources are less effective. This was demonstrated in the first few months of 2025, when there was a prolonged period of unseasonably overcast weather with little wind. This caused both solar and wind energy to be less abundant. During this time, hydropower played a bigger role in meeting renewable energy demand.

Hydropower is particularly valuable during winter months, when there are variable weather conditions. Statistics show that two thirds of hydropower annually is generated in the winter to provide extra energy during peak demand, highlighting its importance as a flexible and reliable source of renewable energy.

What are the benefits and drawbacks of hydropower in the UK?

Benefits                                    

• Fully sustainable – water is natural, renewable, and does not deplete due to being processed by hydropower plants, making it a sustainable source of electricity.
• Near-zero greenhouse gas emissions – hydropower plants in the UK produce a limited amount of greenhouse gases during electricity generation, making it a more environmentally-friendly option than a fossil fuel plant.
• Lower dependency on weather – apart from during times of droughts, hydropower in the UK is generated throughout the year, at all times of the day, in most weather conditions. This makes hydropower a more reliable energy source compared to wind or solar.
• Flood control – hydropower plants, in particular those that use reservoirs, can be effective tools for managing water supplies, through flood controls and river flow regulation.
• Boost to local economy – reservoirs created as part of pumped-storage hydropower plants can be beneficial to the local community, as areas of interest. Activities like rowing and fishing clubs can be organised on the reservoirs themselves, and then other businesses like cafes and fishing shops can be set up close by to take advantage of tourism opportunities.
• Economic benefits – generating energy through hydropower has been shown to reduce costs for consumers in the UK. This is particularly pertinent when other energy sources rise significantly in price. For example, during the 2022 energy crisis, increased reliance on hydropower supply reduced the wholesale price of electricity by £1.1 billion.

Drawbacks

• Land use – both impoundment and pumped-storage plants require large amounts of land for reservoirs to be built, meaning there are fewer suitable sites available for development.
• High initial costs – hydropower sites, particularly offshore sites and reservoirs for impoundment and pumped-storage, have extremely high initial costs involved for infrastructure to be built and connected to the National Grid.
• Long application processes – due to the extensive land use and disruption to the local environment, it can take a long time and be very expensive to plan and approve hydropower sites in the UK.
• Environmental impact – hydropower sites can disrupt the natural environment for fish and local wildlife, either by changing the flow of water or displacing ecosystems.

What is the future for hydropower in the UK?

As of October 2024, the Government announced a “cap and floor” scheme to encourage investments in renewable energy projects. This scheme will provide payments to developers that cannot reach a minimum revenue, in exchange for a share of profits over a certain level. This makes investing in renewable energy projects, including hydropower plants, a much less risky option for organisations.

Following this scheme announcement, 5 new pumped-storage hydropower plant projects have started in the UK, all of which are being built with the aim to increase hydropower installed capacity to 7.7GW by 2035, tripling current capacity. These projects are all based in the Highlands in Scotland and include: Coire Glas, Balliemeanoch, Earba, Corrievarkie and Loch Kemp.

Whilst hydropower in the UK is never predicted to outpace wind, solar, or biomass as a renewable energy source, its expansion remains a key part of the UK’s strategy to meet its 2030 Clean Power targets and 2050 Net Zero goals.

Hydropower, particularly pumped-storage plants, plays an effective role in providing energy to the National Grid during times of variable weather conditions and peak demand. Overall, it is clear that hydropower has great potential in the UK when working in conjunction with other renewable energy sources.