California’s largest electricity provider — Pacific Gas & Electric Co. — has gotten some understandable love from the environmental world recently. It’s part of the U.S. Climate Action Partnership, an enviro/business alliance calling for a national climate plan. It told off (and quit) the U.S. Chamber of Commerce for hating all over clean energy and climate science. And it announced a significant 500 MW solar project last spring.

As more and more companies speak up for clean-energy investment (GE, Google, PepsiCo, John Deere, and the big three automakers did so last week), it’s tempting to sort major corporations into “good guy” and “bad guy” camps. Or at least “gets it” and “doesn’t get it” camps.

PG&E, an investor-owned utility, shows why that doesn’t work. The northern California utility has spent a cool $46 million on a ballot initiative that would protect its market share from encroachment by municipally owned utilities. It’ll have the effect of blocking out power providers that want to make stronger renewable investments than PG&E’s admirable but modest steps.

How it works: Proposition 16, on next Tuesday’s state primary ballot, would prevent local governments from creating or expanding public power services unless they get a two-thirds popular vote. That difficult bar makes it unlikely that cities like San Francisco will be able to form municipal utilities to compete with PG&E.

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Why it matters: It’s a prime example of corporate brazenness in the age of Citizens United — PG&E is using $46 million of its investors’ money to protect its market share from nonprofit challengers. It continues the problem of legislation being made through ballot initiative. It’s contributing to the assault on public services through TV ads that raise fears about “government-run electric service.”

It also prevents one form of clean-energy expansion: community choice aggregation, a method that places like Marin County, Calif., have used to purchase renewable energy. Such methods aren’t the be-all-end-all of renewable investment, but they’re a tool worth defending.

Who cares: A very long list of cities, towns, counties, environmental groups, consumer groups, and editorial boards oppose the measure. So do AARP, the League of Women Voters, and another large private utility, San Diego’s Metropolitan Water District. Of course, none of them have $44 million to compete with PG&E, the measure’s dominant supporter.

“This is a for-profit corporation trying to kill off its not-for-profit rivals,” San Francisco Supervisor Ross Mirkarimi told the San Francisco Chronicle. “Prop. 16 is a colossal fraud perpetrated on the people of California.”

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Says Sierra Club California: “There is a compelling public interest to make it as easy as possible for communities to promote clean energy, reduce pollution and greenhouse gases, and increase local and consumer control over energy decisions. PG&E’s ballot initiative makes a mockery of its self-proclaimed leadership in clean energy and climate protection, places corporate interest above the public good, and makes it more difficult to confront global climate change.”

Paul Tullis at True/Slant has a comprehensive explanation of the campaign, if you’re looking for more.

California already faces an attack on its landmark climate plan financed by two Texas refinery companies. It doesn’t need an attack from a local ally.