-So much more dangerous than nuclear power.

-So much more dangerous [laughter] I met Heather Hoff many years ago when we had young kids and we were doing environmental service projects together.

Then in 2015, we heard that Diablo Canyon was under threat of premature closure.

I was worried about that because it had taken me such a long time to change my mind from being suspicious about the place to then just believing that it aligned with my environmental values because our personal reason for founding Mothers for Nuclear was from an environmental perspective, for land conservation and for climate reasons.

Woman: We tend to be a little hippie, liberal leaning [chuckles] environmentalists.

There weren't a whole lot of people like us working in nuclear, so we decided that we had a special voice, a special perspective that we wanted to share with the world.

Zaitz: We went to a gathering of employees and other people who cared, and we heard, really, more about the threat.

After that meeting, we were the last ones in the room.

We knew we had to do something about it.

We didn't know what yet, so we just started organizing people.

We organized an event at a local brewery.

We had a little silent auction, and we were going to organize a march from San Francisco to Sacramento to tell lawmakers that we needed to keep Diablo Canyon open.

We made all of our own signs and at the end, we showed up at the California State Lands Commission meeting in Sacramento, and we all spoke about what we cared about and we only grew from there.

When Heather and I started Mothers for Nuclear, we were saying something that the company that employed us was not saying, which was, we should keep existing nuclear power plants open.

We knew that public opinion has to change in order to bring about support for policies and politics that support nuclear, and that will then get us to more clean energy.

Nuclear energy is such a powerful hope for me because it's a way that we can power our planet, while still protecting our environment from climate change.

Hoff: I think nuclear is going to be our savior, it's going to be the way that we address climate change, the way that we decarbonize our electricity supply, and the way that we do it with the least impact on our planet.

Mecklin: Climate change is used as part of the argument for all sorts of things.

It's an argument for renewable energy, but a whole set of people are using it as an argument for nuclear energy.

People who came to see this as climate change is so important that the dangers of nuclear power were being overvalued, and its positive attributes in the fight against climate change were undervalued.

They like to present themselves as people who were following the science, not fearmongers.

Narrator: How well nuclear energy contributes to the battle against climate change requires grappling with California's complex energy system.

Penn: California gets its energy from a variety of sources.

Like much of the country, it's primarily natural gas.

It's about 49% natural gas.

Nuclear makes up about 9%.

Solar now is about 20%.

Then you have wind, hydro, and geothermal, which make up about another 20%.

We also receive power from Arizona, Nevada, Oregon, and even as far as Wyoming.

It's about a third of California's supply.

You're depending on the states around you to help keep the lights on.

Mecklin: Even amongst the climate scientists I talk to regularly, there is a split on an renewables alone provide all of the energy needs so that we can go to a low-carbon or zero-carbon energy setup for the United States?

There are times when wind and solar will provide more than 100% of the power that a community needs, but solar and wind don't happen all the time.

Solar power produces electricity when the sun shines.

At night, it doesn't produce, and the wind doesn't always blow.

There are storage methods you can use, it's just, they are nowhere near large or plentiful enough to have, right now, renewable power provide all of the United Statespower.

Penn: We haven't built enough storage, in large part, because all of these issues focus on economics.

Our system, when it comes to energy, is based on a utility company that has a rate base that they draw from to build stuff: the transformer hanging on a light pole to the power plant.

And they rely on their ratepayers to cover those costs.

That makes it difficult because we see rates now rising at a pace all across the country, particularly as we go through the energy transition.

The question is, what is going to fill the gap between what solar and wind can produce, the need for storage, and the move to get rid of fossil fuels?