Page last updated on 19th August 2026
What is hydropower and how does it work?
In this guide, we'll look at how hydropower works and where it is used. We'll also explore the advantages and disadvantages of hydropower as part of a more sustainable energy future.
Hydropower is a renewable form of energy that uses moving water to generate electricity. Water flows through a turbine, causing it to spin and drive a generator. It is one of the oldest ways of producing power, and today it remains an important part of the global renewable energy mix.
Globally, hydropower generates over 50% of renewable energy. In Great Britain, however, it made up just 2% of electricity generation in 2024. Yet how much a country uses it depends on geography, water availability, infrastructure and investment.
What is hydropower?
Hydropower is a form of renewable energy that uses the movement of water to generate electricity. It is also known as hydroelectric power and usually harnesses flowing or falling water from rivers, streams, dams or reservoirs.
Hydropower has been used for centuries, from traditional water wheels to modern hydroelectric power stations. Today, large-scale hydropower plants often use dams and reservoirs to generate electricity for the grid, while smaller micro hydropower systems can use streams or rivers to provide power for individual homes, farms, businesses or local communities.
How does hydropower work?
Most hydroelectric systems are built in places where water naturally flows downhill, such as rivers, reservoirs, lakes or mountainous areas. The basic process is:
Water is collected or directed from a higher point, such as a lake or reservoir.
The water flows downhill through a channel or pipe, often called a penstock.
As the water passes through the system, it spins a turbine.
The turbine drives a generator, which converts the movement into electrical energy.
The electricity is either sent to the grid or used locally, such as in a micro hydropower system.
The water continues downstream, allowing the natural water cycle to continue.
The higher the water source, the more electricity the system can generate. This is why hydropower is often best suited to hilly or mountainous regions with reliable water sources. It also helps explain why Scotland, with its mountainous landscape, generates the majority of the UK’s hydroelectric power.
For more information, check out Energy Saving Trust’s guide to hydroelectricity generation.
Advantages and disadvantages of hydropower
Hydropower can be a valuable source of renewable electricity, but it is not suitable everywhere. The advantages and disadvantages of hydropower depend on a few things. These include the size of the system, the local environment, water availability and how the project is designed.
Hydropower benefits
Like other renewable energy sources such as biomass and wind energy, hydropower has a wide range of benefits:
Renewable, clean energy
Hydropower uses the natural movement of water to generate electricity. Because it does not burn fossil fuels during operation, hydroelectric power produces very low greenhouse gas emissions once the system is running.
Water is also part of a natural cycle, which means hydropower is considered a renewable energy source. As long as rainfall, rivers and reservoirs remain available, hydroelectric systems can continue generating electricity.
Long-term cost-effectiviness
Hydropower systems can be expensive to build or install, but their long-term operating costs are often relatively low once they are in place. This is because they use the movement of water as their fuel source and can operate for many years with good maintenance.
Micro hydropower for homes can be especially cost-effective for rural or off-the-grid homes, farms and businesses that are close to a suitable water source.
Reliable power generation
Unlike solar or wind power, which rely on weather conditions to operate, hydropower systems can provide a consistent supply of electricity when water flow is stable.
Wider water management benefits
Depending on the design and location, some hydropower schemes can provide additional benefits beyond electricity generation. Reservoir-based systems may help regulate water flow, support irrigation, supply water to communities or reduce flood risk.
However, these benefits depend heavily on how the project is planned and managed. Poorly designed schemes can also have negative effects on local ecosystems and water quality.
Disadvantages of hydropower
Here are some potential drawbacks of hydropower:
Geographic limitations
Hydropower depends on access to a suitable source of flowing or falling water. It works best in places with rivers, streams, reservoirs or hilly landscapes. In these places, water can move naturally from a higher point to a lower point.
For homeowners, micro hydropower is only practical in very specific locations. It usually requires reliable water flow all year round, the right permissions and enough height difference to generate useful electricity.
Build or installation costs
Large hydropower facilities can be expensive to build. This is because they often require dams, reservoirs, turbines, generators and major engineering work.
Micro systems are smaller, but they can still entail significant installation costs.
Environmental impact of hydropower systems
While hydropower is low carbon, it can still affect the environment. Large dams and reservoirs can disrupt river ecosystems. This can disrupt fish migrations and other aquatic life.
Micro hydropower systems usually have a smaller environmental impact than larger-scale schemes, but they can still affect natural water flow if they are not carefully designed and managed.
Water availability
Hydropower is generally more predictable than some other renewable energy sources, but it still depends on water availability. Droughts and regional changes in rainfall can reduce how much electricity a system can generate.
This means hydropower works best where water flow is reliable and where the system has been designed around local environmental conditions.
How smart meters can support renewable energy like hydropower
Hydropower and other renewable sources work best when supply and demand are closely matched. That means matching how much electricity is available with how much people actually need at that time.
Smart meters automatically send meter readings to energy suppliers, helping build a clearer picture of how electricity is used across the day. This can support more flexible demand, which makes it easier to use renewable electricity more efficiently across the grid.
They can also enable time-of-use tariffs, where electricity may be cheaper at certain times of day. This can encourage some households to shift use to off-peak periods, helping reduce pressure on the grid and make better use of renewable electricity when supply is high.
Get a smart meter and help Britain use more renewable energy. Simply enter the name of your supplier in the box below to get started.
Hydropower in the UK and its future role
Hydropower in the UK currently makes up a relatively small share of electricity generation, but it still has a role to play in the transition to a low-carbon energy system. The UK’s best opportunities for hydroelectric power are often in areas with suitable landscapes and reliable water flow, such as parts of Scotland and Wales.
Great Britain is working towards net zero by 2050. As part of this, hydropower is likely to support the wider renewable energy mix alongside wind, solar, biomass and other low-carbon technologies. There may be fewer opportunities for new large-scale hydropower projects. But smaller schemes and community projects could help provide local renewable electricity, energy storage and grid flexibility.
Smart meters can also support this transition by helping households across the nation better understand and manage their energy use in a more energy-efficient way.
Get a smart meter to support better use of renewable electricity.
Hydropower FAQs
What is hydroelectric power?
Hydroelectric power is electricity generated using the movement of water. In most systems, flowing or falling water turns a turbine, which powers a generator and produces electricity.
What is hydroelectric energy?
Hydroelectric energy refers to the energy produced by harnessing moving water. The term is often used interchangeably with hydropower or hydroelectricity.
Is hydropower renewable?
Yes, hydropower is renewable because it uses the natural water cycle. Rainfall, rivers and reservoirs can be replenished over time, allowing hydroelectric systems to generate electricity without burning fossil fuels.
How does hydroelectric power work?
Hydroelectric power works by converting the energy of moving water into electricity. Water flows through a turbine, causing it to spin, and the turbine drives a generator that produces electrical power.
How does hydropower generate electricity?
Hydropower generates electricity by using flowing or falling water to spin a turbine connected to a generator. The generator converts the turbine’s movement into electricity, which can then be used locally or sent to the grid.
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