San Francisco passed legislation this week that will require all new buildings under 10 stories tall to be outfitted with solar panels, effective next January. The California city will become the largest municipality in the U.S. with such a mandate.

“By increasing our use of solar power, San Francisco is once again leading the nation in the fight against climate change and the reduction of our reliance on fossil fuels,” Scott Wiener, the city supervisor who introduced the legislation, said in a statement. “Activating underutilized roof space is a smart and efficient way to promote the use of solar energy and improve our environment. We need to continue to pursue aggressive renewable energy policies to ensure a sustainable future for our city and our region.”

The San Francisco Board of Supervisors unanimously passed the ordinance Tuesday. As reported by NPR, the legislation makes explicit references to combating climate change and expresses concern about the city’s future. “As a coastal city located on the tip of a peninsula, San Francisco is vulnerable to sea level rise, and human activities releasing greenhouse gases into the atmosphere cause increases in worldwide average temperature, which contribute to melting of glaciers and thermal expansion of ocean water — resulting in rising sea levels,” the ordinance reads.

Smaller California cities already have similar laws in place.

Beginning in 2017, all new San Francisco buildings with 10 or fewer floors must have either solar photovoltaic or solar water panels. The measure builds on a California law that mandates new buildings have at least 15 percent of their roof space exposed to sunshine for solar panel use in the future.

While some have hailed the news as an important step toward reducing the city’s carbon footprint, Engadget noted the impact could be low, pointing out that not many new buildings being constructed in San Francisco have fewer than 10 floors.