San Francisco has passed a law requiring all new buildings below 10 stories to have solar panels installed on their rooftops. 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."

Other governments around the world have adopted similar policies, including the states of Maharashtra and Haryana in India. Dubai also plans to make rooftop solar panels mandatory for all buildings starting in 2030, as part of the Dubai Clean Energy Strategy 2050. More locally, the smaller Californian cities of Lancaster and Sebastopol introduced compulsory rooftop solar panels in 2013.

San Francisco's new regulations add to already existing Californian laws which require 15 percent of rooftops on buildings of 10 stories or less to be unshaded and solar ready. Under the new law, buildings must have either solar photovoltaic or solar water panels installed, or a mix of the two.

As part of a concerted effort to one day run the city entirely on renewables, the mayor set up a taskforce in 2011 to develop policies and programs that steer it in this direction. It hopes to achieve this goal by 2025.

Source: Scott Wiener