When Joe Seaman, the city planner for the working class town of Cohoes, New York, Googled the term “floating solar,” he didn’t even know it was a thing. What he did know is that his tiny town needed an affordable way to get electricity and had no extra land. But looking at a map, one feature stood out, he said. “We have this 14-acre water reservoir.”

Seaman soon found the reservoir could hold enough solar panels to power all the municipal buildings and streetlights, saving the city more than $500,000 each year. He had stumbled upon a form of clean energy that is steeply ramping up. Floating solar panel systems are beginning to boom in the United States after rapid growth in Asia. They’re attractive not just for their clean power and lack of a land footprint, but because they also conserve water by preventing evaporation.