01/24/2013 01:42 pm ET Updated Mar 26, 2013

California's New Era of Rooftop Solar

A recent story in the Los Angeles Times, "Small-scale solar's big potential goes untapped," tapdanced around an inescapable conclusion about solar power in California without really coming out and saying it: small and rooftop projects may be solar's near-term future.

Yes, it takes thousands of roofs to match one big project like the nearly completed 370 MW Ivanpah solar thermal plant sprawling across the deep Mojave Desert in San Bernardino County. But rooftops have more accessible capacity, and more community benefits, and investments of both money and intention are starting to flow that way.

Just this week, crowdsourcing financier Solar Mosaic announced it had fully funded $300,000 in small-scale and rooftop systems for California affordable housing projects in just 24 hours, offering investors a 4.5 percent return on the money in nine years. It sold like hotcakes.

Take a deeper look at the investment potential by looking at your own roof: In December, Geostellar data became available for Los Angeles County, and I ran an instant, free solar analysis on my house in the Del Rey neighborhood. Just type in your address and the report pops up.

The site projected that I could generate 8,291 kilowatt-hours of juice per year, and save $2,479 in electricity bills per year, or $61,975 over the 25-year life of the system. Plus avert about 111,000 pounds of CO2 emissions. With incentives, it could cost me around $10,000 to install. (You can also do a similar calculation at, which will give slightly different figures.) That's one roof. There are millions more naked roofs just like mine all across the Southland, some of them on Costcos and schools and malls, a vast universe of unrealized energy and savings potential.

A 2012 study commissioned by California's Public Utility Commission acknowledged this gold mine, finding that the state could realize 15 gigawatts of electrical capacity -- that's 15,000 MW -- in Local Distributed Photovoltaics by 2020. That's only eight years from now. LDPV, as it's known, is solar energy generation reducing load at your local substation, and never gets transmitted over the high-voltage wires. It's produced locally and used locally. The biggest chunk of that would be produced by residential rooftop systems.

The study, titled "Technical Potential for Local Distributed Photovoltaics in California," also laid out some technical hurdles that would make that entire 15 GW of capacity difficult to realize, but its message is clear: rooftop systems under 20 MW can provide a majority of local load and represent relatively low-hanging fruit.

And it's not just in California. A 2012 Pike Research report says distributed PV is going to continue to be the fastest-growing segment of the global solar market, growing at a compound annual growth rate of 18 percent out to 2015, with revenues increasing from $66 billion in 2010 to $154 billion.

Energy companies have been struggling to site, build and connect vital utility-scale solar plants deep in California's Mojave Desert, such as Ivanpah, Hidden Hills, or any of the dozens of other large plants proposed for Riverside, San Bernardino and Inyo Counties. When first blueprinted years back, both the solar industry and environmentalists believed this was the way to go, sacrificing the livability of one large chunk of desert in exchange for loads of green power. The Obama Administration is still laboring under this assumption and the federal government has poured $16 billion into utility-scale plants. New data is changing that picture.

While cleaner than the coal-fired plants that once provided most of our power, the big solar plants have run into serious environmental, transmission and financial issues. In a series of stories about big solar that includes the one mentioned above, the L.A. Times has tracked downsizing due to wildlife issues; bitter opposition to new transmission lines that bring this power from the deserts, built at ratepayer expense; and local job and tax revenue figures that have fallen far short of promises.

As an alternative, Gov. Jerry Brown's California Solar Initiative has been driving the rooftop transformation, aiming to install 12 gigawatts of rooftop solar. The California Energy Commission's New Solar Homes Partnership is targeting another 400 MW. The future is distributed. California installed more than 1 GW of customer-generated solar in 2011 and was on track to do better than that in 2012.

Writing about the CPUC study on ClimateProgress, John Farrell of the Institute for Local Self-Reliance notes that, of the four types of small-scale solar (sub-20 MW) included in the study (commercial rooftop, residential rooftop, ground < 10 MW and ground > 10 MW), fully half of the state's 15 gigawatt potential is on residential rooftops. He pulls out four charts to illustrate.

Local PV reduces the load at the source, eliminating environmental and transmission issues and generating local jobs. Plus, residential rooftop owners even get to sell their excess power to their neighbors and be energy producers rather than ratepayers.

Communities are starting to look to their rooftops in order to see their energy future. It's a transformative movement, gaining momentum in California, and the rest of the country may soon follow.