San Francisco just became the first major US city to mandate solar panel installation on new construction. Since 2014, California’s Title 24 energy standards have required that fifteen percent of all commercial and residential rooftops in buildings ten floors or fewer be solar ready. While “solar ready” can mean different things, in the context of Title 24, it means that newly constructed buildings need to consider the feasibility of installing solar panels during the design process, and that there must be a sufficiently large unobstructed and unshaded part of the roof where it would be possible to install solar panels.

San Francisco’s Better Roof Ordinance takes Title 24 a step further, requiring that solar panels be installed on the solar ready roof area, effective January 1, 2017. The new ordinance requires electricity generating panels, solar water heating, or a combination of both. Two square feet of living roof, or “green roof”, can serve as a substitute for one square foot of solar.

Roofs are an underutilized potential source of renewable energy, and the legislation itself is explicit in describing San Francisco’s interest in tapping into energy sources that do not contribute to climate change. San Francisco is a coastal city, and as such, it is especially vulnerable to the results of climate-induced rising sea levels. According to the city’s board of supervisors:

“San Francisco is already experiencing the repercussions of excessive CO2 emissions as rising sea levels threaten the City’s shoreline and infrastructure, have caused significant erosion, increased impacts to infrastructure during extreme tides, and have caused the City to expend funds to modify the sewer system.”

The Department of Environment analyzed proposed construction projects in the third quarter of 2014 and found that the required solar panel installation would avoid 26,000 metric tons of carbon dioxide emissions per year. It would also increase the existing power of the solar electricity systems in place by 7.3 megawatts from 24.8 megawatts. The 7.3 megawatt increase of solar energy can generate enough electricity to power approximately 2,500 homes in San Francisco.

The new ordinance, passed unanimously by the city’s Board of Supervisors, is part of the city’s larger goal of drawing one hundred percent of it’s power from renewable sources by the year 2020. Although San Francisco is the largest US city to require solar panel installation, Sebastopol and Lancaster have mandated solar panels on certain kinds of new construction since 2013.

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