In June, PG&E made waves across the US power sector by announcing it will not renew its operating licenses for the dual-unit 2.2GW Diablo Canyon nuclear plant – California's last operating nuclear station – when they expire in the mid-2020s.

PG&E's decision was slammed by some environmentalists, who believe the gap left by Diablo Canyon could be filled by fossil fuel-fired plants – as has happened in places like Germany when they've moved to phase out nuclear.

Diablo Canyon, located along the Pacific Ocean halfway between Los Angeles and San Francisco, produces a whopping 18,000GWh of electricity each year, equivalent to 9% of California's consumption.

But concerns that Diablo Canyon will be replaced by gas-fired plants were dismissed at Solar Power International by Steve Malnight, PG&E's senior vice president for regulatory affairs, who says California's surging base of renewables – and particularly distributed solar – will soon make Diablo Canyon a relic of the past.

Over the next decade "virtually all of the growth in energy consumption is going to met on customers' premises, through distributed generation and energy efficiency", Malnight said. "In other words, the load on the grid is basically flat."

Meanwhile, California is bringing significant amounts of large-scale renewables online as it races towards its legally binding renewables targets of 30% for 2020 and 50% for 2030, among the most aggressive such targets in the world.

PG&E has no doubts that the 50% target will be met. "It's very achievable – it's not a stretch," Malnight said. "We're well on the way to 50%."

Separately at Solar Power International, Ronald Nichols, president of Southern California Edison, another major California utility, said 30% of the company's 5 million customers will have distributed energy resources – including solar, storage and electric vehicle plug-ins – installed within a decade.

Given the vast amounts of renewables coming online in California, both at the utility-scale and behind the meter, Diablo Canyon would be increasingly expensive and wasteful to operate, Malnight said.

"When you look at what the profile's going to look like in the energy sector in California, a base load facility that generates 24/7, all the time … it just doesn't fit."

PG&E's decision to close Diablo Canyon represented another setback for nuclear power in the US. Only a decade ago, many experts predicted a US nuclear renaissance was on the way, but the sector has been sideswiped by the fracking boom and the rise of renewables.

Question marks hover over the future of nuclear in other countries as well, including the UK, as evidenced by the government's recent demand for more time to consider the controversial 3.2GW Hinkley Point C project.

Malnight acknowledged that PG&E does not yet know exactly how it will replace the 18TWh that Diablo Canyon produces each year, or whether it will even need to.

The utility has already committed to meeting 2TWh through renewables and the same amount through energy efficiency measures.

Beyond those plans, PG&E has committed to sourcing 55% of its electricity from renewables by 2031 – going beyond California's mandate. "We feel [those plans] are already likely to replace Diablo Canyon or at least a significant portion of what's going to be needed," Malnight says.

"If anything else is needed, we have ample time to identify and procure it, and we're committed to doing it on a greenhouse gas free [basis]."