Duke Energy Florida announced plans Thursday to launch a major solar power effort that will produce electricity equivalent to that of a small power plant.

The plan is a surprising move for Duke, which has held steadfast to the idea that solar won't work in Florida without storage because the Sunshine State has too many clouds.

Duke's new position on solar comes as pressure mounts on Florida's investor-owned utilities from homeowners and business owners who want more solar on their rooftops.

Duke's proposal, which was submitted this week to state regulators in the utility's 10-year plan, would substantially increase the state's solar capacity.

Over the next 10 years, Duke proposes to build 500 megawatts of solar power, an amount that is twice the state's current capacity. The utility plans to begin construction on the first 5 megawatts by the end of the year.

"Innovative investments in solar energy will provide customers with more options to use this resource, while diversifying our energy mix and continuing to meet the needs of Florida's growing economy and population," said Alex Glenn, state president of Duke Energy Florida.

Glenn's comment is a departure from his past statements in which he said Florida's clouds thwart solar's effectiveness.

"We are the Sunshine State, but we're also the partly cloudy state," Glenn told state lawmakers during the 2013 legislative session. He added that energy storage from improved battery technology would make solar more viable because it could also provide power when it's cloudy and at night, not just on sunny days.

Battery systems have become a major focus of solar- and wind-generated electricity, but storage still hasn't reached the level that Glenn suggested utilities need.

The change in Duke's approach to solar comes as pressure mounts on Florida's utilities and on Tallahassee from grass roots organizations that are calling on the Sunshine State to live up to its name by tapping the sun for more of its electricity.

Floridians for Solar Choice — a coalition of tea party and Christian Coalition conservatives as well as liberals, environmentalists and retailers — has launched a petition drive to add an initiative to the 2016 ballot that would allow those who generate electricity from the sun to sell the power directly to other consumers.

Such transactions are now illegal in Florida.

If the measure passes, it would create competition for such investor-owned utilities as Duke, Florida Power & Light, Tampa Electric and Gulf Power.

"It's wonderful to see that Duke has found the efficiency which others have now been seeing for a long time in solar being added to any energy plan," said Tory Perfetti, director of Floridians for Solar Choice. "And it's now time to allow the people of Florida to enjoy it as an option in multiple ways, which our ballot initiative gives them the opportunity to do.

"Utility-size solar is one side," he said. "Allowing consumers and businesses to participate as well … is going to be the best for Florida.

Susan Glickman of the nonprofit environmental group the Southern Alliance for Clean Energy praised Duke's plan, saying that the use of solar will save consumers money because the sun provides free fuel.

"Utility-scale solar — along with rooftop solar — will help to move us away from carbon-based fuels like coal," Glickman said. "Given that Florida is dangerously overreliant on natural gas, adding solar will help to diversify the state's fuel mix."

The majority of Florida's electricity is generated with natural-gas plants.

Duke's new solar energy facilities would be in addition to a natural-gas plant the utility is set to build in Citrus County, upgrades to a plant in Polk County and buying another Polk County natural-gas plant.

With little focus on solar, the Sunshine State has fallen behind such other states as North Carolina and New Jersey in deploying solar. Georgia also has contended for a ranking above Florida in solar development.

Since the beginning of the year, Florida utilities have moved to bolster the Sunshine State's solar efforts.

In addition to Duke's projects, FPL announced a plan in January to build three solar farms that would nearly double the state's current solar capacity.

FPL said it had found a "cost-effective" way to expand solar power in Florida and proposed to install the systems at three sites in its service area. The utility proposes to add 225 megawatts of solar to the state's current 229 megawatts by the end of next year in Manatee, DeSoto and Charlotte counties.

Also in January, Gulf Power, the state's smallest investor-owned utility, announced a proposal to build a total of 120 megawatts of utility-scale solar power at Eglin Air Force Base in Fort Walton Beach, Holley Field in Navarre and Saufley Field in Pensacola.

The joint effort among Gulf Power, the Navy, Air Force and HelioSage, the project's developer, will help meet the U.S. Department of Defense's goal of achieving 25 percent renewable energy by 2025.

Contact Ivan Penn at ipenn@tampabay.com or (727) 892-2332. Follow @Consumers_Edge.