The next wave of solar on rooftops

New buildings in San Francisco up to 10 storeys are required to have solar installed from January 2017.
Published: Wed 18 May 2016

With the move towards greater energy efficiency and distributed generation, retrofitting technologies to existing building stock can be costly and time consuming, and in some cases impractical. In new buildings, on the other hand, such measures can be in-built more practically and cheaply, and they are an obvious opportunity for local councils or government to consider, especially as they can be readily legislated.

Such legislation has been around since as far back as the 1980s but it is fast growing in popularity with the need for emissions reductions and the decarbonization of economies and other sustainability considerations globally.

Legislation for PV

In 2008 Culver City in California passed a requirement that all new large commercial buildings should have solar PV. This was followed in 2013 by Lancaster and Sebastopol, which were the first cities in the US to require PV on new residential buildings.

The latest to join this list of California cities, and with stricter requirements, is the largest in the US so far, San Francisco, and the coastal city of Santa Monica, both in second half of April.

Solar for San Francisco

The San Francisco legislation, which was introduced by Supervisor Scott Wiener – and which was passed by the Board of Supervisors unanimously – requires solar PV and/or solar water heating to be installed on all new residential and commercial buildings up to 10 storeys in height constructed in the city from 1 January 2017 on.

This takes a step further current California state law, which requires 15% of the roof area of new small and mid-sized buildings to be “solar ready”, i.e. with no shading and free of obtrusions, to ensure that installations are made.

“Activating underutilized roof space is a smart and efficient way to promote the use of solar energy and improve our environment,” said Wiener, adding that the legislation will help move San Francisco towards its goal of meeting 100% of the electricity demand with renewable energy (aimed by 2020).

In the case of solar PV systems, the capacity must be at least 10WDC per square foot of roof area allocated to the collectors. In the case of solar thermal systems, they will be required to generate annually at least 100kBtu per square foot of the allocated roof area.

This isn’t Wiener’s first piece of new building legislation. Under a previous piece of legislation San Francisco became the first city in the country to require water recycling in new developments. On World Water Day in March, he promised to introduce legislation to require water submeters to be installed in all new residential multi-unit buildings.

PV for Santa Monica

In Santa Monica all new residential and commercial building constructions will be required to carry rooftop solar systems under legislation that comes into effect later this month.

In the case of residential buildings, installations must have a capacity of at least 1.5W per square foot of the dwelling. In the case of multi-family dwellings and other commercial buildings the minimum requirement is 2W per square foot of the building footprint.

“In Santa Monica we are moving away from buildings powered by fossil fuels in favour of clean and cost-effective solar energy,” commented Dean Kubani, Santa Monica’s Sustainability Manager.

The City’s energy and climate goals include reaching carbon neutrality by 2050.

A Santa Monica statement says that the timing of the ordinance capitalizes on market trends in the solar industry. With the decreasing cost of solar, the cost-benefit ratio is strong. The City’s requirements are estimated to increase upfront construction costs for a single family home by 2.8% on average, while reducing long term electricity costs by 65% on average. For multi-family homes, the numbers are 0.5% and 24% on average respectively, and on commercial properties, 0.75% and 11% on average.