You know what’s fun? What’s fun is watching young people figure out how to change the world they’ve inherited.

Case in point: Billy Parish. When I first met him, he’d just dropped out of Yale. Not because he couldn’t hack it. Because he didn’t think it was as important as fighting climate change. And so he built the Energy Action Coalition, the nationwide student mobilization against global warming. And he built it in a particular way, as a coalition of like-minded groups on hundreds of campuses — he was charismatic, but he put his charisma to use helping to leverage many disparate voices into one force.

As he got older, he let others take over the student movement, and he went to work looking for practical solutions to the same crisis. Given his skills and drive, he could have become a conventional entrepreneur, starting some solar start-up that would make deals and build projects and collect revenues. But his basic sense never wavered: What we needed was a way for communities to work together.

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And so, Monday, Solar Mosaic starts accepting investments. If you live in New York or California, or you are an “accredited investor” in other states, you can invest money; it will be used to put up solar panels on a grand scale, and the revenues will pay you a nice rate of interest. It’s a way, one of the first, to put lots of individuals’ money to work building the future we need.

To me, it’s far more exciting than the news that Warren Buffett just bought a couple of California solar plants. Yes, that’s good confirmation that the solar business is a strong one — that it makes sense to the guys with the green eyeshades, not just the wild-eyed greens. But if we’re going to take this to scale, it’s going to require unleashing even more money than Buffett controls — it’s going to take a society-wide effort. You can see something like it underway in Germany, where the Energiewende drive has put solar panels on top of millions of roofs — most of them paid for and owned not by big utilities but by small cooperatives and churches and the like.

As of Monday, investors will be able to put their money into the roof of a New Jersey convention center — but also the roofs of two affordable housing projects in California. (As the good book notes, the sun shines on rich and poor alike). I’ve already got a solar panel on my own roof — I’d look to put one on somebody else’s. (And I wouldn’t mind making 6 percent on my investment, which is Solar Mosaic’s going rate).

Right now the student movement that Billy Parish helped spark has grown to epic proportions — on 192 campuses students are demanding that their boards of trustees divest their holdings in fossil fuel companies. If they succeed, it will help a good deal, for we need ways to reduce the political power of those companies who are holding back the future.

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And it will help even more if they take those funds and put them into projects like Billy Parish’s — actuarially sound, ecologically sound, and spiritually sound. Building community is at least as important as building solar panels. If we can do both at the same time, we’ve got a fighting shot at a workable planet.

UPDATE, 1/8/13: Solar Mosaic sells out first round of public investments in less than 24 hours.

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