State officials often hail a mandate that’ll ensure a third of California’s energy comes from renewable sources.

What they don’t always clarify is that they’re not talking about getting that power from sources like this:

Photo by Jamie Scott Lytle
Photo by Jamie Scott Lytle

They’re talking about big projects that are usually dozens and even hundreds of miles away from the utility’s most densely populated coverage areas. Like this:

Jim Sulley/newscast
Photo by Jim Sulley/newscast

Solar projects topping rooftops across San Diego aren’t directly helping the state and San Diego Gas & Electric reach the 33 percent state target known as the Renewable Portfolio Standard, a law first introduced in 2002 that’s been accelerated multiple times.

Though state rules technically allow rooftop customers to sell their so-called renewable energy certificates to utilities, San Diego Gas & Electric and the state’s other utilities say a separate Public Utilities Commission ruling has made doing so virtually impossible.

And that has left SDG&E with less of an incentive to help residents get rooftop solar systems and more of an incentive to take another approach.

Most of the projects that are helping SDG&E ramp up its renewable content are in Imperial County and eastern San Diego County.

SDG&E provided this map of power sources it’s factored into its quest to meet the so-called RPS mandate. The utility says its current power mix is 32 percent renewable and expects to reach the 33 percent target later this year.

Image courtesy SDG&E
Image courtesy SDG&E

These aren’t small-scale projects. We’re talking acres of solar panels that produce lots of power.

Eleven solar projects in San Diego County can generate about 59 megawatts of energy. Six larger-scale projects in Imperial County produce up to 789 megawatts.

To put that in perspective, solar experts told me a single megawatt of solar production usually requires four to six acres of land.

And those massive solar panel installations that SDG&E’s relying on to help meet its state mandate can generate enough mega wattage to power more than 183,000 homes, a figure based on one industry estimate.

Three other projects in the California desert and Arizona power another roughly 27,500 homes by the same measure.

Let’s compare that with rooftop solar. SDG&E reports that the on-paper capacity of the region’s rooftop solar is about 369 megawatts from about 54,400 customers – and they’re consuming much of the energy they produce themselves.

The utility does get one benefit: That production ostensibly reduces the amount of total power SDG&E has to buy though it’s not clear how much. That’s a piece of a big debate we’ll explore later.

And certainly, the region benefits from energy sources that emit fewer greenhouse gases.

But whatever power those rooftop panels are producing wouldn’t be a cost-effective way for SDG&E to meet its renewable goals – even if the rules made that workable.

That was never the intent of the Renewable Portfolio Standard, anyway.

Rooftop solar panels were pricier when the state kicked off the program in 2002. Most Californians couldn’t afford them. So state policymakers saw utility-scale solar projects and other renewables as a better way to go. The standard was meant to push utilities to invest in those. Others incentivizing rooftop solar panels came later.

The RPS framework hasn’t changed much since and the economics of large-scale solar allowed utilities to more quickly add renewables to their mixes at a lesser cost.

Sure, multiple solar developers told me, the cost to get that energy to the more-populated coastal areas may be higher with far-flung solar projects but looking far east opened up more land and presented fewer development roadblocks. (San Diego has little open space to spare and frequent fights over development.)

Plus smaller projects don’t move the renewable needle as much and can require more manpower and logistics to coordinate, said Victor Vilaplana, SDG&E’s vice president of electric and fuel procurement.

“This is really about cost and output and there’s just no way you’re going to do better on a bunch of distributed resources (rather) than a utility-size resource,” Vilaplana said.

There’s a hitch here that often gets mentioned by folks who aren’t so fond of SDG&E: Utilities profit from infrastructure projects rather than energy sales per state regulations. In other words, if they have to build something, they can pass the cost along to ratepayers. Profitable projects include transmission lines connecting far-flung renewable projects to the local grid.

Scott Anders, director of University of San Diego’s Energy Policy Initiatives Center, and other energy researchers said transmission costs may add to the cost ledger but large-scale solar further east pencil out better anyway.

“The structure of the RPS is driving utilities to try to find the least-cost renewable,” Anders said. “The industry’s response is you build big plants and they’re cheaper.”

The equation could be changing, though.

State lawmakers are now eyeing a 50 percent renewable energy mandate that’s spurred debate about whether rooftop solar should play a larger role under a new system. After all, rooftop systems are cheaper and more popular than ever.

For now, though, utility-scale projects dominate. As of today, just 15 solar projects are on tap to supply half the power capacity SDG&E’s citing to meet its renewable target – and none of them are on rooftops.

This is part of our quest on whether solar will pay off for San Diego. Check out our previous post, Questions (and a Few Answers) About Going Solar in San Diego, here.

Lisa is a senior investigative reporter who digs into some of San Diego's biggest challenges including homelessness, city real estate debacles, the region's...

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