California broke its record for renewable energy when solar and wind provided enough to meet all consumer demand. At the time, natural gas power plants were still on, a necessity for the grid.

Transcript

SCOTT SIMON, HOST:

California hit a major milestone for clean energy last weekend. For part of an afternoon, the state produced enough renewable energy to meet 100% of demand for the first time. But that doesn't mean fossil fuels are going away quickly. Solar and wind power have been booming, but getting off fossil fuels completely could take decades, even in California. Lauren Sommer from NPR's climate team joins us. Lauren, thanks so much for being with us.

LAUREN SOMMER, BYLINE: Hi there.

SIMON: Even if only for a moment, how did California set the record?

SOMMER: So California has been installing a lot of wind and solar. Renewables have more than tripled in the last 15 years. And the day that record fell had ideal conditions. The sun was shining, the wind was blowing, and it wasn't too hot yet, so the state didn't need a huge amount of power for air conditioners. But there's a catch. Natural gas power plants were still running at that time. California was making more power than it needed, so it was sending some out of state. So technically it was enough renewable energy for 100% of demand in state because even if California wanted to, it can't actually turn off all the natural gas power plants.

SIMON: Why can't they turn them off if they're getting enough from solar and renewables?

SOMMER: Yeah. It has to do with a very tricky time of day, which is when the sun sets. All that solar power goes away quickly, and California has to replace it with something. Natural gas power plants fill in that gap, but that means a lot of them run all day because these huge industrial facilities take hours to turn on. So if you need them in the evening, you can't turn most of them off, even if you have solar power you could be using instead.

SIMON: California's looking at other technologies that might replace natural gas?

SOMMER: Yeah, and that's mostly giant batteries. So the idea is to store solar and renewable energy in batteries during the day and then use it later in the evening when it's needed. Batteries are growing, but they're still a small fraction of what's needed. So when I talk to fossil fuel companies in California, they don't sound too nervous. Alex Makler is a vice president at Calpine, which runs a number of natural gas power plants.

ALEX MAKLER: We very much support, you know, new technologies and innovation and decarbonizing the grid. But there are certain things that the natural gas fleet, you know, does very well and that cannot be easily or, at this point, economically replaced.

SIMON: So what does this mean for California's goal to become carbon neutral? Is there a projection for how long fossil fuels will still be here?

SOMMER: Yeah, that's what's interesting here. California has led the country in climate change policy. You know, the state's trying to reach 100% carbon-free power by 2045. Energy experts I speak to, you know, like Mark Specht at the Union of Concerned Scientists, say that renewables and batteries have come a long way and they're going to keep making progress.

MARK SPECHT: We should be doing everything we can to build huge amounts of solar, huge amounts of wind, huge amounts of energy storage. And that's going to get us at least, like, 90% of the way there to a clean grid. It's really that last 5 to 10% where it starts to get much harder.

SOMMER: That's because there are rare events, like, you know, going many days without sunshine or wind where you would need something else. That could be energy storage that lasts a long time. It could be using natural gas power plants if you're burying the carbon emissions underground so they don't warm the planet. You know, California's really a bellwether in this quest to go carbon-free. And it shows even where there's been a lot of progress, the road to fully eliminating fossil fuels is, you know, still being figured out.

SIMON: Lauren Sommer from NPR's climate team, thanks so much for being with us.

SOMMER: Yeah, thank you.

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Tags: fossil fuels  renewable energy  CAlifornia