Reinventing hydropower: Can the oldest renewable stay relevant?

Posted: March 31, 2026

Hydropower has long been the biggest source of renewables-generated electricity, but this decade, solar and wind look set to overtake it. In the next five years, global hydropower is expected to grow by 154 GW, a much slower rate than the hydropower boom of the early 2000s. The International Energy Agency warns that policymakers must do more to support hydropower, given the critical role it plays in keeping electricity grids secure and stable.

Hydro projects face wide ranging pressures, from mounting controversy surrounding new sites —particularly around displacement of people and biodiversity concerns, to old sites beset by aging infrastructure. Recent years have produced a flurry of reports about climate fluctuations and droughts that are changing water levels, drying rivers and impacting power grids.

In 2024, Ecuador faced drought-induced blackouts lasting up to 14 hours, while a record-breaking drought in China in 2022 led to rationed electricity. Last year, headlines warned that low rainfall had impacted Norway’s hydro reservoirs, threatening the power market across northern Europe. For the countries that rely on hydropower for the majority of their electricity generation, including Norway, this is particularly concerning. More than a billion people live in countries where more than half their electricity comes from hydro.

With the pressures mounting, could hydropower’s reign be coming to an end?

A short history of hydropower

Unlike other renewables, hydro can be used to provide stable baseload power. And it has been doing so for over a hundred years.

In Northeast England, engineer and industrialist William Armstrong is thought to have been the first person to combine electricity and hydropower, merging the two inventions to light his house in 1878. A visionary who predicted that fossil fuels could not be relied on indefinitely, Armstrong’s house was considered a “magician’s palace” by contemporaries. Water from a lake powered a machine that pumped water into a reservoir above his house. Gravity fed the water back into the house, providing plumbed water and powering a hydraulic lift and electric lighting.

Just a few years later, in the U.S. state of Wisconsin, the Vulcan Street Plant became the first plant in the world to generate electricity by combining hydropower sites with one of Thomas Edison's new electrical generators. The plant provided electricity to private and commercial customers, illuminating the nearby towns.

By 1900, hundreds of small hydropower plants were in operation across the globe. Countries embraced hydropower, and mega-projects like the Hoover Dam helped to meet growing energy demand. A post-war construction boom saw utilities build state-owned hydropower plants across Europe and Japan, providing critical electricity capacity.  

Mega-dams and the debate over large hydropower projects

Today, China’s Three Gorges Dam—the world’s largest power station by nameplate capacity (the total amount the facility is designed to produce when operating at max capacity) —is so enormous that it actually slows down the Earth’s rotation by fractions of a microsecond. It generates around 0.3 TWh electricity a day, enough to power 3 million households for one month. The concrete gravity structure is over 2,000 meters long and creates a huge reservoir to contain water, driving 32 turbine generator units.

While mega-dams generate vast quantities of green electricity, they’re not without critics. In previous decades, build costs often spiraled out of control, sometimes creating years of debt for emerging economies. Large dams can also have a huge impact on the people and environment that surround them: the BBC reported concerns that China’s planned Motuo Hydropower Station dam will impact millions of people living downriver, as well as the environment. The project will include five cascade hydropower stations, producing an estimated 300 TWh of electricity annually, roughly three times the annual capacity of Three Gorges.

Across the Pacific Ocean, another mega-dam sits on the Brazil/Paraguay border. The Itaipu Dam supplies almost 90% of Paraguay’s electricity and about 15% of Brazil’s with 20 generator units. The Itaipu plant has generated more electricity than any other dam in history—over 3,000 TWh since it started operating in 1984.

Like China’s dams, it faced criticism for displacing up to 60,000 people and flooding ecosystems, as well as corruption scandals that caused its construction to run far over budget. Today, the dam operators work to improve the sustainability of its artificial lake and conserve 100,000 hectares of the Atlantic Forest that surround it.

Small hydro in the community

Hydro doesn’t always have to be mega. Across the world, communities are managing to reap the benefits of reliable, green power without the cost, disruption and environmental impact of a mega-project. Less invasive run-of-the-river hydropower projects—which use the natural flow of a river to spin a turbine and don’t require a dam—are gaining traction and can help provide electricity to remote locations. Because these smaller hydro projects don’t have dams or storage they can be more impacted by climate fluctuations and seasonal river flow variations.

In northern Uganda, the Achwa I and 2 run-of-the-river hydro projects have a capacity of 42 MW each, and sustainably generate about 375 GWh (or 0.375 TWh) over a year in an area with low electrification. Climate fluctuations that cause drier spells have impacted electricity generation at Achwa, but these can be somewhat mitigated by combining it with solar generation. Last year, African Business reported that Africa currently has around 7GW of power capacity from run-of-the-river schemes, with plans for an additional 11GW of run-of-the-river projects on the continent.

In the Philippines, micro-hydropower is helping some of the 3.6 million households that aren’t connected to the national grid. Villages are turning to small renewable energy generators, building their own generators in areas that are inaccessible by road. NGO SIBAT has helped local communities construct and manage 28 micro-hydro generators in the country, each providing power to about 75 previously off-grid households on average.

In Oxford, U.K., another community has built its own hydropower system, which generates enough electricity to power 60 homes. The money to pay the build costs (of just £690,000) was raised by the community, who to demonstrate the role that community energy can play in reaching net zero.

Why aging hydropower plants need upgrades

Close to 40% of the global hydropower fleet is over 40 years old, and aging hydropower plants are starting to pose challenges. Three years ago, the International Renewable Energy Agency reported that “The global hydropower fleet is reaching a tipping point, where a large share of the installed capacity will soon require upgrades, refurbishment or possibly retirement.”

Europe, North America and Oceania in particular have older hydropower fleets after a building boom in the 60s and 70s.  The IEA reports that between 2020 and 2030, $127 billion will be spent on modernizing aging plants. Refits also need to consider how waterflows, environmental and water regulations may have changed since the plant first opened.

Several big upgrade projects have already been announced. In the Scottish Highlands, the Kinlochleven hydropower plant, built in 1909 and with a 19.5MW capacity, is set for an upgrade. At the Nedre Røssåga power plant in Norway, a 1950s plant was modernized with an additional 100MW of power, including swapping the existing six small turbines to three small and one large, for more variability in power supply. An E.U.-funded initiative, ReHydro, is aiming to refurbish and modernize European hydropower, including using digitalization tools that monitor and analyze critical hydropower components and sensor information.

Charles Hunsucker, president of Power Systems at Rehlko, a global company focused on energy resilience told Power Magazine that these infrastructure upgrades are important “as energy systems grow more integrated and decentralized. [...] The most resilient energy infrastructure will be built by aligning legacy assets with emerging innovation, creating a more resilient and secure backbone for tomorrow’s electrified economy.”

Legacy and innovation: Reinventing hydropower for energy resilience

Combining innovation with legacy is essential to hydropower’s survival. In Norway and the U.S., hydropower plants are adopting digital twins of their aging plants to monitor their assets and help simulate and plan for droughts and floods. Data centers are increasingly co-locating with hydropower, in some cases making use of hydroelectric facilities that were built for industrial uses that no longer exist. And while wind and solar rapidly scale, pairing them with hydro can provide an effective mitigation to the climate impacts that affect all renewables—where drought stops hydro generation, the sun may well be shining on solar panels. These diversified power sources can build global energy resilience.