Harnessing the energy of flowing water

Conventional hydroelectric plants harness the energy produced by flowing water, using simple mechanics to convert the energy into electricity. Water falling from an elevated reservoir drives turbines to generate electricity. Because it uses water as a fuel source, hydroelectricity is inexpensive and environmentally friendly to produce. However, the amount of power that can be created by hydroelectricity is limited by the volume of water held by the dam in storage.

Duke Energy began its operations in the Carolinas as a hydroelectric company. As the population and industry grew, water power alone could no longer supply all the electricity needed. Today, our hydroelectric plants provide a small but important part of electricity in the Carolinas – mainly during short periods when power use is high, such as hot summer days and cold winter nights. The electricity produced by hydroelectric plants is available to meet customer demand within a few minutes.

content wide conventional hydro plant


The water is held in a reservoir, or lake, behind the dam.


Penstocks lead the water into a chamber housing the turbine. The water is held at a higher elevation than the turbine so that it can fall with enough force to strike the turbine’s blades and cause it to spin.


The turbine wheel is attached by a shaft to a system of magnets and wires called a generator. As the turbine rotates, these magnets and wires also spin – producing electricity.

Draft tube and tailrace

The water returns to the river by passing through a draft tube under the turbine and into the tailrace.


Frequently Asked Questions

  • One advantage of using water to generate electricity is its low cost. Hydroelectricity is cheaper than electricity produced in coal-fired and nuclear power plants. This is because the fuel – water from rivers and lakes – is free. Water, unlike coal and uranium, is also a renewable resource. And since the fuel does not need to be burned, producing electricity from hydropower does not produce emissions.

    Another advantage of hydropower is that the potential energy in water can be stored until it is needed to produce electricity. Then, it can be quickly converted to kinetic energy by allowing the water to flow into the turbines. The turbines spin, and the generators produce electricity in minutes.

    Quick start-up times make hydroelectric plants ideally suited to provide peaking power. Hydroelectric plants can provide electricity in seconds at times when customers need it most.

    In addition to ensuring a reliable supply of hydroelectricity for our customers, the lakes created by our hydroelectric plants provide communities with recreational opportunities, such as boating, fishing and swimming. The lakes also sustain wildlife habitats and offer water sources for everyday use to local communities.

    At Duke Energy, we work in partnership with regulatory agencies, local communities and environmental organizations to protect and conserve environmentally sensitive areas around our lakes and to ensure an adequate stream flow to balance these many interests.

  • One disadvantage to hydroelectric power is that it necessitates the building of dams. While the reservoirs dams create can provide numerous recreational opportunities (e.g., boating, water skiing, and fishing), their creation floods large areas of land, eliminating wildlife habitats.

    Additionally, while operating costs for hydroelectric plants are relatively low, the initial building costs are very high. Building large dams is both costly and difficult, making new hydroelectric plants an unattractive option for electric companies. Also, most suitable sites for hydroelectric generation have already been developed. In fact, the Catawba River, located in Duke Energy’s service area in the Carolinas, is one of the most electrified rivers in the world.

  • Over a century ago, the founders of our company had a vision: Let the powerful, 225-mile Catawba River energize a thriving Piedmont Carolinas. In 1899, Dr. Gil Wylie received permission to build and operate a hydroelectric plant at India Hook Shoals near Fort Mill, S.C. In 1904, the rope-driven waterwheels of the “Old Catawba” Hydroelectric Station turned generators for the first time, electrifying the grist and textile mills along the Catawba River Valley.

    Soon afterward, tobacco magnate James Buchanan “Buck” Duke provided Wylie the capital for what later would become Duke Power. Great Falls Hydro, the company’s oldest operating hydroelectric station, started operation a few years later in 1907. A newer Catawba Hydroelectric Station replaced the “Old Catawba” plant in 1925. In 1960, both the station and the lake it impounded were renamed in honor of Dr. Wylie.

  • Today, hydroelectric plants are used mainly as peaking plants. These plants are designed to run for short periods of time when customer demand for electricity is high. When customers need power, Duke Energy’s hydro plants can be started up and begin generating electricity in only a matter of minutes.

    Although hydroelectric generation makes up a small percentage of Duke Energy’s total generation mix, it is a critical part of our diverse generation mix.

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