Floating solar panels placed on reservoirs around the world could generate enough energy to power thousands of cities, according to a study published last week in the journal Nature Sustainability.

Called floating photovoltaic systems, or “floatovoltaics,” these solar arrays function the same way as panels on land, capturing sunlight to generate electricity. They sit on a floating platform and are kept in place by cables connected to the bottom of the body of water, writes Wired’s Matt Simon. The new research shows this buoyant technology has the potential to create vast amounts of power and conserve water—without taking up precious space on land.

The scientists considered how much electricity could be produced if 114,555 reservoirs around the world had 30 percent of their surface covered with floatovoltaics, capped at 30 square kilometers of coverage per reservoir. They estimate that, globally, the panels would generate over 9,000 terawatt hours of energy per year—around 2.4 times the amount of electricity the United States consumed in 2021.

“That’s remarkable,” J. Elliot Campbell, a co-author of the new paper and an environmental engineer at the University of California, Santa Cruz, tells Wired. “It’s about ten times today’s generation from solar. And solar is growing like crazy. If there was ever a time to ask where to put all this stuff, it’s now.”

A handful of countries are already answering that question by using floating solar panels in a limited capacity, including Brazil, China, India, Indonesia, Singapore, South Korea, Thailand and Vietnam. California plans to test a similar idea in which solar panels will be placed above irrigation canals.

If local floatovoltaics are adopted further, 6,256 cities across 124 countries could fully satisfy their electricity needs, the researchers found. This could largely benefit smaller towns: A little over 70 percent of these cities have a population under 50,000, while more populous cities might not have as much space on reservoirs to alone support their large populations, the authors note.

The five countries that would generate the most electricity from introducing or expanding the use of floating solar panels are the U.S., China, Brazil, India and Canada. The U.S. could produce almost half its 2021 electricity consumption by using floating solar with the study’s restrictions—on 30 percent of reservoirs, not exceeding 30 square kilometers on each one.

Beyond electricity generation, floating solar panels could conserve an estimated 106 cubic kilometers of water per year, close to the amount used annually by 300 million people. That’s because the panels create shade and reduce the water temperature, leading to less evaporation, according to Ars Technica’s John Timmer. Amid severe drought in several parts of the world, this could provide some relief.

In turn, the water can cool the solar panels, making floatovoltaics as much as 15 percent more efficient than solar panels on land, which produce less power and need more maintenance when they overheat.

While solar panels on land are a clean source of energy, they take up a lot of space. They use land that could otherwise serve agricultural or habitat conservation purposes, according to the Verge’s Justine Calma.

“Land use is becoming a big issue for renewables. People are worrying about competing uses of land, and in some markets, you might struggle to find land,” Lara Hayim, head of solar research at BloombergNEF who was not involved in the study, tells Bloomberg’s Carly Wanna. “So in those places, there is a bit of an incentive to build on water.”

Still, floating solar panels do have some downsides. They cost 25 percent more to install than systems on land, Sika Gadzanku, an energy technology and policy researcher at the National Renewable Energy Laboratory who peer reviewed the new paper, tells Bloomberg. They might also reduce oxygen levels in water, which could hurt fish, and the panels may negatively impact water quality.

“We really need additional research on what some of the potential impacts are, thinking about these water ecosystems,” Gadzanku says to Wired.