Renewable Energy Sources

What Is Hydroelectric Power & How Does It Work?

Gexa Energy
April 26, 2023
minutes read
Gexa Energy
Publication Date:
June 1, 2023
Last updated:
June 8, 2023

You’re likely familiar with the Hoover Dam, one of the largest hydroelectricity plants in the United States, but it’s far from the only one. In fact, hydropower plants can be found across the country in a variety of sizes, from massive dams to much smaller systems.  

Hydropower—the use of naturally flowing water to generate electricity—is one of the most commonly used renewable energy sources in the U.S. and throughout the world. In 2019, hydropower accounted for more than 18% of the world’s energy generation.  

But how does hydroelectric power work? And is it a viable part of the global clean energy solution?  

Read on to learn about hydropower, the plants that produce electricity, and the many benefits of this renewable resource.

Related: Learn all about renewable energy benefits.  

What is Hydropower?

Also known as hydroelectric power or hydroelectric energy, hydropower uses moving water to produce electricity. One of the oldest and largest renewable energy sources in the world, the use of hydropower dates to ancient times. More than 2,000 years ago, the Greeks used water wheels to grind wheat into flour.

Today, hydroelectric energy accounts for over 30% of renewable energy generation in the United States and is responsible for about 6% of the country’s total electricity. Forty-eight states utilize hydroelectric energy to generate electricity to power homes and businesses.  

Hydropower is used worldwide, with top-producing countries including China, the United States, Brazil, Canada, India, and Russia. The largest hydropower plant in the world is the Three Gorges Dam in China, which holds back the Yangtze River and boasts enough generators to produce 22,500 megawatts of electricity.  

Related: Explore other sources of renewable energy.  

How is Hydroelectric Energy Produced?

Hydroelectric power plants typically include:

  • A reservoir of water – This can be a large body of water like a lake or as small as an irrigation ditch.
  • A gate or valve that controls how much water flows out  
  • A place where the water goes after flowing through the gate

Right before water flows down a hill or over the top of a dam, it gains potential energy. This potential energy is then converted to kinetic energy as the water flows down into the hydroelectric facility.  

A hydropower plant generates electricity much like a coal-fired power plant. Both use a power source to turn the blades of a hydraulic turbine, which then turns a shaft in a generator to produce electricity. The main difference is that, instead of using fossil fuels, a hydropower plant uses the natural movement of flowing water as a power source to turn the turbine’s blades and generate electricity that can then be distributed to the facility’s customers.  

Related: Explore other types of renewable energy and learn about wind power.  

Types of Hydropower Plants

There are three main types of hydroelectric power plants: impoundment, diversion, and pumped-storage facilities.  

An impoundment facility is the most common type of hydroelectric plant. In this configuration, a dam controls the flow of the water, which is stored in a reservoir. A gate allows more water to be released through the dam when more energy needs to be produced.

A diversion facility doesn’t use a dam but a series of canals to send flowing water to the turbines that power the electricity generator.

A pumped-storage facility collects clean energy and stores electricity for future use by pumping water from a reservoir at a lower elevation to another at a higher elevation.  


What Does Hydropower Cost?

Hydroelectric energy is a more cost-effective source of power than many other sources. Many states that primarily use hydropower to produce electricity, such as Idaho, Washington, and Oregon, have lower energy bills because this renewable energy source takes advantage of moving water.

While building a hydropower facility and dam requires some large upfront costs, maintenance and operations are lower than many other energy sources. Plus, the long lifetime of a hydropower plant allows these costs to be spread out over time.  

Related: Learn about solar power, another source of clean and renewable energy.  

The Pros and Cons of Hydropower

The advantages of hydropower are significant, which is why it’s been used as an energy source for thousands of years.  

In addition to being a clean and cost-effective form of energy that doesn’t produce any greenhouse gases, hydropower plants can send power to the grid immediately, making them a reliable source of backup power during a blackout or major outage.  

Building dams for hydropower facilities also provides other benefits outside of generating electricity by helping to control flooding, assist with land irrigation, and establish water supplies.  

Unfortunately, one of the disadvantages of hydropower is that constructing new plants can have a negative impact on the environment by pushing out local wildlife. But hydroelectric power facilities are so long-lasting that new constructions are few and far between.  

Related: Learn about nuclear energy, an often-misunderstood source of clean electricity.

Final Thoughts  

One of the oldest and most reliable forms of clean energy, hydropower is a key part of the strategy to reduce global reliance on fossil fuels and support a healthier environment. With many hydroelectric power facilities already in place, this renewable energy source already helps power our homes and businesses and, in partnership with other power sources like wind and solar, will continue to help limit our use of nonrenewable resources like coal and natural gas.  

Gexa Energy offers residential energy plans 100% powered by renewable energy sources*. Learn more about our monthly electricity plans and join us in supporting renewable energy, creating a cleaner, healthier world.  

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Gexa Energy purchases renewable energy credits (RECs) from renewable generation resources throughout North America to match 100% of the energy sold under your electric plan. The RECs Gexa purchases represent the renewable attributes of power generated from a variety of renewable energy sources, including, but not limited to, the sun, wind, geothermal, hydroelectric, wave or tidal energy, and biomass or biomass-based waste products, including landfill gas.