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California Cities Have Barely Scratched The Surface Of Their Residential Solar Potential

Danny Kennedy Posted by Danny Kennedy.

Danny is a global authority on environmental issues and a successful clean-tech entrepreneur.

California Cities Have Barely Scratched The Surface Of Their Residential Solar Potential

Sungevity used proprietary Instant iQuote technology to evaluate the solar potential of three major California cities, and the results may surprise you.

Sungevity’s technology analyzed rooftops in San Diego, San Jose and Berkeley and estimated that the three cities have barely scratched the surface of their residential solar potential. Sunny San Diego leads the pack in existing residential PV capacity with an estimated 70.7 megawatts installed already, but the Southern California sunshine remains a huge untapped resource: Sungevity projects that San Diego could install 2,000 megawatts of PV capacity on suitable residential rooftops, meaning the city has only used 3.5% of its residential solar potential.

The innovators in San Jose, by comparison, are making better use of Silicon Valley’s solar potential (5.8%) but the city still has a long way to go to realize its full potential. Berkeley, one of the original thought leaders in solar policy, trails the two, only making use of 2.5% of its projected residential solar potential.

“The only way is up,” says Steve Atherton, chief technology officer at Sungevity. He stresses that Sungevity’s analysis of solar potential for San Diego is not calculated on the back of an envelope, but is based on very specific house-to-house data. Sungevity’s Instant iQuote (iiQ) technology uses satellite imagery and LIDAR data to model residential rooftops and automatically design a Sungevity solar system on each suitable one. This technology can be applied to individual homes, when a homeowner is looking into solar options, or can be applied on a huge scale, like an entire city (2).

“It’s the opposite of a shot in the dark. We use quality imagery and numerous other data points to get an accurate picture house after house. So, if a tree blocks the sun or a chimney lowers the square footage available for panels, our numbers reflect that. We are talking about the real aggregate solar potential San Diego could harvest tomorrow,” says Atherton.

San Diego’s Residential Solar Potential Is through the Roof

Using iiQ, Sungevity evaluated 352,000 individual homes and determined that 71% of all San Diego residential rooftops are suitable for solar. If each of these households went solar, their solar panels would have a combined generating capacity of 2,000 megawatts. Sungevity’s technology estimates that all those solar panels could produce 4.8 billion kilowatt-hours of electricity annually for San Diego, enough to cover 145% of the city’s annual residential electricity consumption (3).  That means if San Diego were to realize its projected residential solar potential, rooftop solar panels could power every household in San Diego and still have over 1 billion kilowatt-hours to spare!

San Diego has pledged to go 100% renewable by 2035 and Sungevity’s data shows that the city could easily cover its residential electricity use if it maximized its residential solar potential.

San Jose: A Solar Force To Be Reckoned With

Glittering solar panels on every street say it all: Silicon Valley darling San Jose is also at the forefront of solar in the US. Last year alone, solar capacity on its roofs jumped 34% to 141 megawatts according to Environment America, making San Jose the city with the fifth highest concentration of solar systems in the nation. That means the city installed roughly 13 megawatts of new residential solar capacity in 2015, or roughly 7 new solar systems each day (4).

Despite these impressive numbers, Sungevity’s iiQ analysis shows that San Jose’s rooftops can do even better. After analyzing the solar potential of 222,000 individual homes in San Jose, the iiQ technology found that 77% of San Jose’s roofs are suitable for solar. Combined, they offer space for 900 megawatts worth of solar panels, enough to generate 1.3 billion kilowatt-hours of electricity annually (5).  With the installed solar capacity on San Jose homes currently at about 53 megawatts, the city has reached 5.8% of its full residential solar potential. This is more than Berkeley or San Diego, but still a fraction of the solar capacity San Jose could be housing.

San Jose aims to receive 100% of its electricity from renewable sources by 2022. Reaching its full residential solar potential can greatly help the city realize that goal.

Berkeley Still Has Plenty Of Space To Shine

Berkeley has all the right ingredients for solar. 77% of its residential roofs are suitable for solar panels. The city has a proud history of solar innovation and research. Still, its position is slipping: cities like San Diego and San Jose now leave Berkeley behind.

Berkeley was once a true solar pioneer. The city was the first to offer its residents a no-money-down option to buy a solar system through Property Assessed Clean Energy (PACE): a groundbreaking and much-copied innovation that fueled the demand for solar.

Although installed solar capacity in Berkeley tripled from 2008 to 2014,  it still lags behind cities like San Jose and San Diego. With installed solar capacity on Berkeley homes currently at about 2.3 megawatts, the city has only reached a modest 2.5% of its full residential solar potential. Based on Sungevity’s iiQ analysis, Berkeley’s residential rooftops could potentially house 90 megawatts worth of solar panels, enough to generate 132 million kilowatt-hours of electricity each year.

Will You Help Your City Reach 100%?

Sungevity’s research shows that residential solar presents a huge opportunity for cities across California. The question is: which city will be the first to realize it?

If you’re interested in going solar, whether you live in Berkeley, San Jose, San Diego, or any of Sungevity’s other service areas, you can get a free iQuote here.


(1) Estimated based on the total installed PV capacity of each city reported by Environment America and assuming that 37% of solar capacity in California is residential.
(2) Sungevity’s proprietary Instant iQuote technology combines LIDAR, point cloud data, high resolution aerial imagery, and real estate parcel data to develop a model of the roof at a property address. Projected system details, including estimated system size and annual solar production, are developed from that modeling.  These estimates and a home’s ultimate suitability for solar are not guaranteed. Actual system size and annual solar production will vary based on several factors, including weather, shade, and the final solar system design a customer selects.
(3) Calculated based on Total # California Households, # of San Diego residents, average size California household  (source: US Census Bureau), Total Residential Power Consumption California (source: US Department of Energy)
(4) Calculated based on average system size in San Jose of 5.3 kilowatt (estimate Sungevity)
(5) Among individual factors per house Sungevity’s calculations take into consideration are shading, roof obstacles, house positioning, local solar irradiance and local sun hours.

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