"It's kind of like I'm uniting every warring group in the state," said Jim Gonzalez, the former San Francisco supervisor who's behind Proposition 7, the Solar and Clean Energy Act of 2008.

The opposition comes as a surprise to Gonzalez and Peter Sperling, son of John Sperling, the billionaire founder of University of Phoenix and a longtime supporter of liberal causes. Peter Sperling already has put $3 million into the initiative campaign.

The measure requires all California utilities to generate at least half their power from alternative energy sources such as wind, solar, biomass and geothermal by 2025, well above the 33 percent level Gov. Arnold Schwarzenegger wants to see by 2020. Utilities currently must reach a 20 percent goal by 2010.

Prop. 7 also sets penalties for companies that don't meet the goals and puts a 3 percent cap on consumers' power bills.

"This does no harm to the environment and only toughens up the rules we have now," Gonzalez said.

Gonzalez signed up some early support for his measure, including that of Art Torres, state Democratic Party chairman, and polling showed that voters liked the idea of increasing the amount of renewable energy use in California.

But Gonzalez began hearing rumblings that several environmental groups were unhappy with the initiative, which they argued was poorly written and so complicated that it could hurt the cause of renewable energy in the state.

The groups, many of which had been working on energy legislation for years, were never really brought into the initiative effort, said Ralph Cavanaugh of the Natural Resources Defense Council.

"There was very late consultation," he said. "We asked them last November to step back and take a look at the measure, but by then they already had a finished product."

The initiative sets up such a detailed plan for dealing with renewable energy and siting and building the new, greener power plants that it opens the way for many unintended consequences, Cavanaugh said. Even groups closely involved with renewable energy, such as the Center for Energy Efficiency and Renewable Technology, have lined up against Prop. 7.

"If you're going to legislate at the ballot box, keep it simple, don't write 70 pages," he added. "Our objection isn't to their good intentions, but to their bad initiative."

When Gonzalez went before state Democratic Party leaders last month to seek the party's endorsement, he found the green lobby had beaten him to the punch. Torres pulled his support before the meeting and the environmental groups, which have plenty of support in state Democratic circles, were working hard against the initiative.

Despite support from former state Sen. John Burton of San Francisco and former Whittier (Los Angeles County) state Sen. Martha Escutia, the Democrats voted overwhelmingly to oppose Prop. 7.

"It originally sounded like a good idea, but then people in the party started hearing that environmental groups had problems with the initiative," said Bob Mulholland, a consultant for the state party. The measure's backers "had a lot of good people, but they didn't have what the 'No' side had."

Even without that endorsement, however, Gonzalez has a measure that calls for increased solar power at a time when oil prices are at record highs and a chief supporter with pockets that are deep enough to pay for an all-out fall campaign.

Convincing voters the initiative is a bad idea won't be easy, Cavanaugh admitted.

"It needs to be very clear that the environmental vote on this issue is the 'No' vote," he said.

To make that argument - and raise the millions needed to spread that story across the state - could require the strangest of bedfellows, however.

The main opposition group to Prop. 7 describes itself as "a coalition of environmentalists, renewable energy companies, taxpayers, labor and utility companies."

But despite that wide-ranging list of supporters, the only money in the opposition campaign's kitty includes $645,000 from Pacific Gas and Electric Co., $475,000 from Southern California Edison and $104,000 from Sempra Energy, all regular targets of state environmental groups.

Environmental groups will speak for themselves against Prop. 7 as the campaign moves along, Cavanaugh promised.

Still, Gonzalez is baffled by the opposition he's receiving for a measure he is convinced will make California less dependent on oil, coal and other depletable resources.

"The environmental groups say we're disrupting good stuff that's already going on, but our increase will be over 17 years, so it's not like it's going to be done overnight," he said. "If someone has a better idea, show us."

E-mail John Wildermuth at jwildermuth@sfchronicle.com.

This article appeared on page B - 1 of the San Francisco Chronicle