In general, California has taken two approaches to boosting the solar energy produced in the state. The first is large, utility-scale facilities, often located in the state's extensive desert areas. The second is more ad-hoc, as companies and private citizens are able to install panels on their buildings and facilities if they choose to. But what if the two approaches were merged, with massive deployment of solar on pretty much every bit of developed land in the state? According to a new analysis, the end result would dwarf the state's electricity needs—and probably leave enough to spare to handle its water needs through desalination.

The authors of the paper, all based at Stanford, note that a bit over eight percent of the golden state has already been modified by humans. The authors designated these areas as "compatible" with solar development, although the analysis was a bit more complicated. Concentrated solar power was excluded from areas that are built up, leaving those using photovoltaics only. Over a third of the modified terrain is also urban open space, which could support concentrating solar but consists primarily of a combination of parks, private yards, and golf courses.

Were it not left open, the open space could generate about 26,000 TeraWatt-hours annually. Low-intensity build areas could add another 14,000, while heavily developed regions would add another 3,000. Concentrated solar would provide lower total numbers, but they have the advantage of generating power through the evening demand surge that occurs as people return home from work.

Of course, people might balk at the idea of seeing every bit of open space in their neighborhoods covered in panels. So the authors analyzed the rest of the state, prioritizing 10 km-wide corridors near roads, along with 10 km surrounding high-voltage transmission lines and excluding any protected areas. These areas added another 175,000 TW-hr of photovoltaic capacity.

While those numbers are unrealistic—we're not going to cover all of every urban area with panels—a single number puts them all in context: California's electricity consumption in 2012 was a meager 2,231 TW-hr. Thus, even limiting installations to heavily developed areas would result in a capacity that would easily surpass the entire state's demand and allow the state reach its goal of having a 33 percent renewable grid by 2020. Even adding a small fraction of the low-intensity build area would easily allow the state to supply all of its power via solar, even when solar's capacity factor is considered.

That doesn't mean the state could actually go completely solar. Storage for excess electricity, other than pumped hydro, isn't especially economical, and California is notably lacking in hydro availability. Solar could, however, clearly allow it to shift a lot of its generation to renewables. And it's always possible that a clever use for excess electrons will become apparent once the electrons are actually available.

Nature Climate Change, 2015. DOI: 10.1038/NCLIMATE2556 (About DOIs).