California Gov. Jerry Brown has set an ambitious new energy goal: getting the most populous state in the nation to derive 50 percent of its electric power from renewable sources in the space of 15 years.

But can it be accomplished? And can it be done without sending electricity bills through the roof?

Depends on who you’re talking to.

“We must demonstrate that reducing carbon is compatible with an abundant economy and human well-being,” Brown told the legislature. Hydroelectricity and nuclear power cannot count toward the 50 percent goal.

California already has a mandate that 33 percent of electric power consumed must come from renewable resources by 2020.

The renewables industry cheered the announcement from the 76-year-old Democrat who is entering his fourth and final four-year term as governor. Republicans and business groups had reservations.

“I’m told by the industry that we might be able to absorb 40 percent, but you start having problems” beyond that, state Senate Republican Leader Bob Huff told reporters after Brown addressed the state legislature Jan. 5.

“The sun doesn’t shine at night, so solar doesn’t work. The wind doesn’t blow when you need it, it blows when it does. So you’re left with an unstable grid when you get beyond a certain level.”

“Is it feasible? Absolutely,” said Ken Johnson, vice president of communications at the Solar Energy Industries Association. “With 8,544 megawatts of electricity, solar is already producing enough electricity to power about 2 million homes in California—and we’re just scratching the surface of our potential.”

Senate President Pro Tem Kevin de León, D-Los Angeles, said the goals are “in the realm of possibility.”

Brown said the 50 percent mark could prove to be “a very tall order.”

Count Robert Michaels, professor of economics at Cal State Fullerton University, as skeptical.

“I think it’s going to be a lot more costly than anyone’s making it out to be,” Michaels said, citing what energy economists call the “rebound effect.”

That occurs when something—such as electricity—becomes more available, efficient and affordable, people use more, rather than less.

“Renewables are going to have to be somehow reliably backed up with conventional power sources, and that means we’re back in the fossil fuel-burning business,” Michaels said in an interview.