Skip to Content

Hydroelectric power: how it works

Hydroelectric power harnesses the natural energy of water flowing from a higher elevation to a lower one by the pull of the earth’s gravity. It is not only a renewable and clean energy source, but it also helps us moderate electricity rates.

Discover how water power works and how Ontario Power Generation harnesses it, to benefit Ontarians.

Hydroelectricity: falling for the power of water

Learn the basics of how water produces electricity and why it's such a great source of power.

Hydroelectric stations

Hydroelectric generating stations are like factories that convert the energy of moving or falling water into electricity.

Water flowing from a higher elevation to a lower one, called a “drop,” creates speed and power.

Hydro stations often use the natural drop of a river, such as a waterfall or rapids, as a natural source of water power. Other stations use a dam built across a river to raise the water level to provide the drop. A third type, called ‘run-of-river,’ has no drop and instead uses just the natural flow of the river and thus minimizing its impact on the surrounding environment.

Ontario Power Generation has stations of all three kinds within our hydroelectric generation portfolio.

How hydroelectric stations work

A cross section of a dam.Water collects at the higher level in the forebay, where it enters through the station's intake into a pipe, called a penstock, which channels it down toward the turbine.

The turbine, like a water wheel, turns with the flow and pressure of water from the penstock and as it turns, it spins a generator.

Cross section of water exiting a hydro station through the tailrace.Inside the generator is a rotor with large electromagnets attached to it. As the rotor spins within a coil of copper wires called a stator, this produces the flow of electrons in the stator we know as electricity.

The flow of water, having served its purpose, exits the station through the tailrace where it rejoins the river.