The problem, as Dawn Weisz saw it back in the mid-2000s, was straightforward. She and other residents of Marin County wanted green power. But only 16 percent of the electricity that PG&E, the local utility, was delivering to its 250,000 customers was renewable.

Frustratingly, Weisz and other community members didn’t have any say about what went into that mix. The county government—for which Weisz worked at the time—had set ambitious decarbonization goals and had found that cleaning up their power supply would be the best first step forward. But they couldn’t force the utility to go green any faster.

So she and others organized to form a “community choice aggregator,” or CCA—a nonprofit that took over buying electricity for Marin