Hydroelectric Energy

Ontario Power Generation | CC BY 2.0

➡️ HYDROELECTRIC POWER – The World's #1 Renewable Energy Source

Hydroelectric energy uses dams and reservoirs to harness the power of water in motion. It is the most common form of renewable energy, providing 50% of global renewable capacity. It accounts for 15% of the world's total electricity generation.

Although hydropower is a green alternative to fossil fuels, there are many costs to consider, especially for large-scale dams. Their construction causes very serious and permanent environmental and social damage.

Jump straight to our guide on ➡️ Hydroelectric Energy

Explore our comprehensive resources on -

• Rivers and dams
• The Three Gorges Dam, China
• Renewable Energy Guide
• The Energy Transition

Impoundment, diversion, and pumped storage are the three main types of hydropower plants. The most common method of power generation involves the construction of dams on rivers. Water is released from the reservoir, which flows through turbines, spinning generators to produce power.

China accounts for 30% of global hydroelectric output and is home to the world's largest hydropower plant. The Three Gorges has generators capable of producing a gigantic 22.5 GW of power. Brazil, the U.S., Canada, and Russia also have huge hydropower installations.

Rawpixel | Carol M. Highsmith’s America

PROS -

• Hydroelectric power is clean. Hydro plants do not produce any air pollution or greenhouse gases during operation.
• It provides a consistent and stable supply of power. Plants are capable of meeting large-scale energy demands with a predictable output that can be adjusted to meet electricity fluctuations.
• They consistently outperform intermittent renewables such as solar and wind installations, providing essential grid stability.
• Once a hydroelectric complex is constructed, the costs of operation and maintenance are relatively low. The average cost of electricity from hydropower projects in 2022 was $0.06 per kWh, making it the lowest-cost source of electricity in many markets.
• Hydroelectric facilities can operate for decades, even up to a century, as dams and hydro plants are built to be incredibly durable.
• Dams can help with water management for irrigation, water storage, and flood control purposes. They can also provide locations for recreational activities such as fishing and boating.

Rawpixel | Carol M. Highsmith’s America

CONS -

• Building hydroelectric facilities requires substantial upfront investments. In 2022, the average cost of building hydroelectric power plants worldwide was about $2,881 per kW of installed capacity. The cost varies massively depending on size and location. Projects are known to run millions over budget and years beyond their original timelines.
• Hydroelectricity is geographically dependent. Large quantities of water and land are needed for projects to be feasible.
• Manmade reservoirs drastically alter the natural environment and landscape, often resulting in adverse environmental effects. They reduce river flows, raise water temperatures, degrade water quality, cause sediment buildup, destroy habitats, and affect aquatic life.
• They cause large-scale displacement of communities. Between 40 and 80 million people have been displaced directly as a result of dams and reservoirs. Communities that live downstream are affected even more severely as they suffer from food insecurity and flooding, which threatens their homes and livelihoods.
• Some hydro plants are major emitters of carbon and methane due to the decomposition of underwater vegetation.
• The risk of catastrophic failure, although rare, is disastrous. Dam breaching results in massive flooding and large-scale loss of life downstream.
• Hydroelectricity is highly vulnerable to the effects of climate change, namely drought. Reduced water availability significantly affects power production and water supply to downstream users.

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The Future of Hydropower

New turbine technology will make hydropower more flexible and powerful, but as our climate changes, so does the viability of mega-dam projects. Droughts are becoming more frequent, and in the past few decades, we have seen a significant reduction in hydropower generation.

Declining water levels at the Hoover Dam in the U.S. have resulted in a 25% reduction in energy production. In Brazil, reservoir levels have fallen by more than half in the past 20 years and are currently at just under a third of their capacity.

Heavy rain and flooding also pose major problems. In 2019, severe flooding following Cyclone Idai damaged two major plants in Malawi, cutting off power in the country for several days.

Due to their enormous cost and the social and economic impacts, even countries with vast potential for hydropower generation are cautious about untapping the full potential of hydroelectricity. Careful management of these factors and consideration of future climatic conditions are crucial for the sustainable development and operation of hydroelectric power.

Author: Rachael Mellor, 12.02.25 (Updated 04.06.26) licensed under CC BY-SA 4.0

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