WATER SECURITYRooftop Solar Cells Can Also Help Water Conservation

By Karl Leif Bates

Published 21 September 2022

Energy generation and use are tightly bound to water consumption, and fossil-fueled electrical grid’s enormous water use is often overlooked. A given household may save an average 16,200 gallons of water per year by installing rooftop solar.

Electricity-generating rooftop solar cells not only save on planet-warming carbon emissions, they also save a significant amount of water, say a pair of Duke University researchers who have done the math.

A given household may save an average 16,200 gallons of water per year by installing rooftop solar, they found. In some states, like California, this saving can increase to 53,000 gallons, which is equivalent to 60 percent of the average household water use in the U.S.

You won’t see the savings on your home water bill, but they’re still important.

That’s because energy use is tightly bound to water consumption. Electrical energy production in the U.S. consumes nearly as much water as the agricultural sector. But that figure doesn’t include the additional water used produce fossil fuels in the first place, nor to manage coal ash waste.

“To generate electricity for the grid we need to mine and burn coal, frack and pump natural gas, and cool nuclear plants, all involving high volumes of water that is continuously lost,” said Avner Vengosh, a Duke University distinguished professor of environmental quality in the Nicholas School of the Environment and co-author of a new paper that appears Sept. 19 in Science of the Total Environment.

“However, with the solar cell, it’s a one-time consumption of much a lower volume of water for manufacturing,” Vengosh said. “And then, once it’s installed, there’s no longer any water use coming from that for the next 25 years of expected use.”

Currently, more than 70 percent of the world’s solar panels are being made in China, so the water consumption to generate solar energy occurs overseas.

Co-author Erika Weinthal, a professor of environmental policy in the Nicholas School, said  that to understand the broader water impacts from solar panel production, it is vital to look at the entire supply chain across the world.

“From a contamination point of view, solar cells have huge potential for environmental damage,” Vengosh said. “It contains heavy metals, some of which are very toxic, and therefore they could have impact on the immediate environment where the manufacturing occurs.”

But after that, the water consumption of solar is zero.