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Two Californian Cities Vying For Solar Capital Of The US

Originally published on RMI Outlet.
by Devi Glick

The fight for the title “Solar Capital of the U.S.” is on, and for two towns in California, things are heating up faster than a solar panel during summer peak! Earlier this year Lancaster, on the edge of the Mojave Desert north of Los Angeles, became the first city in the U.S. to mandate solar on new buildings. Months later and 400 miles away, Sebastopol—not far from Napa and Sonoma—followed suit. On the surface they couldn’t be more different … one a conservative, blue-collar city; the other a pocket of liberal, small-town wine country charm. Yet the sun unites them.

When their respective measures passed, both mayors echoed the importance of the mandates in addressing climate change. “The one thing we have to recognize is just how desperate this situation is with global warming, and at the same time recognize that we can actually fix it,” said Lancaster’s Mayor Parris. In Sebastopol, Mayor Keyes echoed the same underlying concern for global climate change: “I think it is the obvious way to go. Every time you build a house you’re making the matter worse.”

Requiring that all new houses install solar panels, or are designed to be solar ready at the time of construction, does have many cost advantages. Up until now, most solar mandates have only required new-build homes to be solar ready (California, Arizona), or at the very least, offer the option of solar ready to customers (Colorado, New Jersey) but they have stopped short of actually requiring the installation of solar panels on the roof. This is where Lancaster and Sebastopol are different.


Lancaster and Sebastopol were the first two cities in the U.S. to pass a solar mandate of this kind, but demographically and geographically, they are worlds apart. Both are in sunny California, but as the prevalence of solar installs in Germany (a country with worse solar resource than those almost anywhere in the lower 48 of the U.S.) shows, solar resources are not the only significant factor driving solar adoption. There was almost no pushback when the measures were proposed, perhaps not all that surprising for liberal Sebastopol, given Sonoma County’s climate goal of reducing GHG emissions 25 percent below 1990 levels by 2015, but eye-opening in Lancaster, given the city’s largely conservative constituents.



In Lancaster, the mandate says that all new residential homes on lots of 7,000 sq. ft. (≈ 1/6 acre) or larger must install a solar system of 1.0–1.5 kW. In Sebastopol, all new residential and commercial buildings are required to install 2 watts of power per square foot of insulated building area or offset at least 75 percent of the building’s annual electric load. Based on the median house size in the western U.S. of 2,150 square feet, that is approximately 4.3 kW per home, or at least 3–4 times as much per home as in Lancaster (and likely even more when taking into account the fact that the solar array needs to offset at least 75 percent of the buildings electricity load).

Despite Sebastapol’s stronger per-house mandate, the absolute impact is much smaller than that of Lancaster. Two hundred new homes are forecasted to be built in Lancaster this year, which means that at minimum 200–300 kW of solar will come online in Lancaster as a result of new buildings, and likely even more if housing developers find that there is strong demand for solar among new-home buyers in the area. In Sebastopol only 16 new homes were built per year in both 2010 and 2011, so assuming that trend continues, that works out to around 70 kW (again, at the mandated minimum) of solar coming online in Sebastopol as a result of new buildings.


My call is a draw. There are so many ways to evaluate the claim of solar capital: based on the strictness of the mandate, the total quantity of solar installed, the quantity of solar installed per house or per capita, etc… Sebastapol’s mandate is more efficient at achieving the goal of minimizing the impact of each new house built, but is in a location where few new homes are actually being built, and the ability of residents to invest in solar without mandates is high. Frankly, the recent mandate is rather secondary to their solar position (as of 2011 in any case) as the #1 solar city in California in installs per resident. Lancaster’s mandate is more flexible, and it will affect many more homes, but the per-home impact will be smaller, which seems reasonable considering the lower ability of its citizenry to provide funds for solar. In addition, Lancaster’s actions are much more eye-opening considering the city’s medium-income status and political make-up.

This is not to say that a solar mandate is always the best option to achieve new-build real estate with low carbon impact. A city can mandate efficient home design, via enforced, high-quality building codes, to reduce the energy needs of a new house by the equivalent of the 1-kW solar panel from the start. Or it could build solar gardens throughout the city to bring online enough renewable generation capacity to offset a portion of energy needed for new builds, while taking advantage of solar gardens’ economy of scale. When cities have their own municipal utilities, a very broad array of market-driven efficiency and renewable generation choices at the distributed level can be unleashed with the right utility programs and price signals. Choosing such options depends on a region’s technical, economic, electrical system control, and political context and constraints. For Lancaster and Sebastopol, these mandates may indeed be their best option, and in the perception fight for “Solar Capital of the U.S.”, they have created winners out of both cities.

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Since 1982, RMI (previously Rocky Mountain Institute) has advanced market-based solutions that transform global energy use to create a clean, prosperous and secure future. An independent, nonprofit think-and-do tank, RMI engages with businesses, communities and institutions to accelerate and scale replicable solutions that drive the cost-effective shift from fossil fuels to efficiency and renewables. Please visit for more information.


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