Did you know that hydroelectricity is the world’s biggest source of renewable energy? According to recent figures from the International Renewable Energy Agency (IRENA), it represents 40% of total capacity, ahead of solar (28%) and wind (27%).
This type of energy is generated by hydroelectric power stations, which are essentially large dams that use the water flow to spin a turbine. They can also serve secondary functions such as flow monitoring and flood control.
To help you learn more about hydropower, we’ve visualized the five largest hydroelectric dams in the world, ranked by their maximum output.
The following table lists key information about the five dams shown in this graphic, as of 2021. Installed capacity is the maximum amount of power that a plant can generate under full load.
At the top of the list is China’s Three Gorges Dam, which opened in 2003. It has an installed capacity of 22.5 gigawatts (GW), which is close to double the second-place Itaipu Dam.
In terms of annual output, the Itaipu Dam actually produces about the same amount of electricity. This is because the Parana River has a low seasonal variance, meaning the flow rate changes very little throughout the year. On the other hand, the Yangtze River has a significant drop in flow for several months of the year.
For a point of comparison, here is the installed capacity of the world’s three largest solar power plants, also as of 2021:
Compared to our largest dams, solar plants have a much lower installed capacity. However, in terms of cost (cents per kilowatt-hour), the two are actually quite even.