An all-renewable energy grid ‘definitely feasible’ for California. But at what cost?

California already gets about one-third of its electricity from solar, wind and other renewable energy sources, and appears on its way toward hitting the 50 percent mark in another decade or so.

But creating an all-renewable electricity grid — completely free of traditional energy from natural gas or other fossil fuels — could be a monumental task.

Stepping up California’s efforts to combat climate change, the state Legislature on Wednesday passed SB 100, requiring utilities to generate all their electrical power from renewable sources by 2045. The Senate voted to approve the bill 25-13, one day after the Assembly narrowly passed it.

Authored by Sen. Kevin de León, the legislation goes to Gov. Jerry Brown, who’s generally been a leader on global warming initiatives but hasn’t said whether he’ll sign it. California would become the second state with a 100 percent renewable electricity mandate, joining Hawaii, which also established a 2045 deadline.

SB 100 is opposed by the likes of Pacific Gas and Electric Co., which noted that renewable energy tends to be more expensive than traditional power — and accused the state of trying to eliminate greenhouse gas emissions “on the backs of electricity customers.”

PG&E spokeswoman Lynsey Paulo also faulted the Assembly for imposing a green-energy mandate without first making sure that utilities will be stable enough financially to “shoulder these new mandates in the face of growing wildfire risk.”

PG&E has been pressing for legislation to alleviate utilities’ wildfire liabilities in the aftermath of last year’s deadly wine-country fires, which could cost PG&E billions in damages. The Legislature is expected to vote late Friday on a bill that would allow PG&E to pass on some of the costs to ratepayers, partially shielding shareholders. Consumer groups have blasted the bill as a bailout and its passage isn’t guaranteed.

SB 100 is a significant step up from current law, which requires California utilities to generate 33 percent of their electricity from renewables by December 2020 and 50 percent by 2030.

As of 2016, the last year for which figures were available, PG&E and the other two big investor-owned utilities — Southern California Edison and San Diego Gas & Electric — already generated nearly 35 percent of their electricity from renewables, according to the energy commission.

SMUD, the Sacramento Municipal Utility District, has procured enough renewable energy to hit the 33 percent mandate by 2020, said spokesman Christopher Capra.

A recent report by the California Energy Commission said wind and solar costs have dropped significantly in the past decade, and are now within shouting distance of fossil fuel prices. PG&E and the other big investor-owned utilities spent an average of 10.1 cents per kilowatt hour obtaining renewable energy last year, a half-penny higher than what they spent on electricity from fossil fuels, the report said.

Creating an all-renewable grid “is definitely feasible,” said Severin Borenstein, faculty director of the Energy Institute at UC Berkeley. “The question is, how expensive is it going to be.”

Californians pay on average a total of 15.2 cents per kilowatt hour for electricity, or about 50 percent above the national average, according to the U.S. Department of Energy. On the other hand, Californians use roughly half as much electricity per capita as the average American, according to California Energy Commission data.

He added that forecasting the future price of electricity 27 years from now is next to impossible. “You have to be realistic about how little we really know,” he said.

Borenstein said the biggest obstacle to hitting 100 percent will be storage. Natural gas-fired plants, which account for 33 percent of the state’s electricity, can be ramped up and down as demand fluctuates. But wind power can only be generated when it’s windy; solar power only works when it’s sunny. They can’t be stored up, and sometimes supply doesn’t conveniently sync up with demand.

For instance, Borenstein said wind generation is most plentiful at night — when skies tend to be windier — but that’s when electricity consumption drops. Solar matches up better, but there are still times when demand is high but supply is scarce, such as early evening.

That doesn’t mean going all-renewable will be impossible, though. Borenstein said California’s “knowledge economy” is the perfect laboratory for investing and perfecting new technologies that could solve the problem.

“We could get new technologies for storage that we haven’t even thought of yet,” he said. “That’s exactly what California should be doing, and is good at.”

In that sense, he said the real benefit of SB 100 is as a spur to innovation. California barely accounts for 1 percent of the world’s greenhouse gases; by itself the state can’t make a real dent in global warming. But if the state can master the technological challenges of an all-renewable grid, it can show the way for other states and countries.

“If it turns out we figure out ways to do this cost effectively, that is going to ripple out ... and move the rest of the world toward getting off fossil fuels,” Borenstein said.