A political group founded by billionaire brothers Charles and David Koch wants Georgia's utility regulators to reject a plan requiring Southern Co. to buy more solar energy, but an Associated Press review ahead of a vote on the issue finds that it has used misleading figures to build its case.

The Georgia chapter of Americans For Prosperity has said in mass emails and on Twitter that a proposal requiring Southern Co. subsidiary Georgia Power to buy more solar energy could raise energy bills by 40 percent. A review of those figures shows the claim is misleading, and there's a debate over how much solar energy might cost.

Georgia's Public Service Commission will meet next week to vote on the utility's plan for meeting Georgia's energy needs for the next two decades. Georgia Power has already agreed to add 270 megawatts of solar energy to its system and did not propose adding more in its latest plan. Commissioner Lauren "Bubba" McDonald Jr. wants a vote on a plan requiring Georgia Power to add another 525 megawatts of solar energy.

McDonald's plan has support from a group of solar developers earlier spurned by Georgia Power and organizers of the Atlanta Tea Party Patriots.

"It's an opportunity for the consumers," McDonald told the AP. "It's an opportunity to utilize what God has given us, and that's the sun."

The Georgia chapter of Americans For Prosperity wants McDonald's plan rejected over concerns it will raise costs.

Solar power has historically been pricier than traditional fossil fuel sources for around-the-clock energy, though costs have fallen and developers argue it is now more competitive. Better figures will emerge once Georgia Power signs contracts as part of earlier pushes to obtain solar power. The company expects to pay no more, if not less, for that solar power than it would pay to get it elsewhere, Georgia Power spokesman John Kraft said.

Even if costs are higher,

the total solar power that has been proposed or added to Georgia Power's system is the equivalent of 1 percent of its current electric fleet, according to AP calculations based on the capacity of the company's power plants and a federal study predicting how reliably different types of power plants can produce electricity. As a result, it is unlikely so small a resource could have a 40 percent impact on monthly bills.

In an email to supporters, Georgia director for Americans for Prosperity Virginia Galloway wrote, "What if I told you something you're not even hearing about in the news is about to raise your electricity bill by more than 40 percent and reduce the reliability of every appliance and electronics gadget in your home? That's what will happen when your Georgia Public Service Commission (PSC) votes on July 11th if you don't take action today!"

To support her claim, Galloway cited a study by the Institute for Energy Research showing that customers in states that require utilities to buy renewable energy paid an average of 39 percent more than customers in states without those rules, such as Georgia.

That is not an exact comparison because many factors — not just solar technology — influence prices. The demand for energy and the available supply affect prices. So does local weather. So does choice: In some places, consumers can pick their own electricity provider. In other places, they must rely on a monopoly. And renewable energy requirements vary greatly among the states that have them.

"It's hard to say it would be fair to apply that across the board," said Liz Coyle, deputy director of Georgia Watch, a consumer advocacy group that supports renewable energy but is wary of consumer cost increases.

Galloway acknowledged in an interview that the pending proposal would "probably not" raise bills by 40 percent, though she said cost increases are possible. She said Georgia Power already has too much spare electric capacity — a point raised independently by other observers — and said that government mandates can create extra expenses in the long run. Click on their website solaronlamp for more information.