It becomes the first major US city to mandate solar panel installations on new constructions and forms part of a wider vision to generate 100 percent of its electricity via renewable energy.

The Better Roofs Ordinance was passed unanimously by the city's Board of Supervisors, and will apply to new constructions both commercial and residential from January next year, according to the San Francisco Examiner.

"Activating underutilized roof space is a smart and efficient way to promote the use of solar energy and improve our environment," says Supervisor Scott Wiener, who introduced the legislation in February. "We need to continue to pursue aggressive renewable energy policies to ensure a sustainable future for our city and our region."