Darden Restaurants Inc. dedicates today a new array of solar panels that is so large it creates a canopy over the four-story parking garage at the company's headquarters in south Orange County.

It is, essentially, a utility-scale power plant, rated at 1.1 million watts.

It also counts as a new point on the timeline of alternative energy in Florida.

A major milestone in the state's energy outlook was reached three years ago when electricity generated by rooftop solar panels began to surge through the giantOrange County Convention Center. What made that flow of electricity especially noteworthy was that the county, working with Orlando Utilities Commission and the Florida Solar Energy Center, had installed enough solar panels to reach the eye-opening, million-watt mark.

At the time, however, a 1-megawatt, rooftop system was seen as achievable mostly as a public-works project supported by taxpayers.

"We looked at solar in 2007, and it was cost-prohibitive," Darden spokesman Rich Jeffers said.

So the company proceeded with building its $152 million headquarters — just a few miles east of the convention center, on the BeachLine Expressway — and opened the 469,000-square-foot facility without solar in late 2009.

But the solar-energy industry has been noteworthy for two trends: making panels that are more and more efficient and able to pump out more current, and making panels that are getting less and less costly.

Jeffers said Darden took another look at solar energy in 2010 and concluded that it had become worthwhile economically — and the right thing to do for social and environmental reasons. A Jacksonville-based contractor, Kenyon Energy, installed the first of 4,404 panels in September and finished the job 105 days later, covering both the garage and part of the main building.

When Darden officials dedicate the canopy of panels today, they will be standing under the largest privately owned solar array in the state.

At a cost of $5.6 million, it could pay for itself within 10 to 12 years, "depending on weather," Jeffers said. Progress Energy, the utility that serves Darden's headquarters, will give the company a conservation rebate of $260,000.

Darden's solar plant is designed to produce 1.9 million kilowatt-hours of electricity a year. That's enough to supply more than 160 homes or, more to the point, as much as 20 percent of the electricity used at company headquarters.

The convention center's array, slightly smaller than Darden's, has been producing about 1.5 million kilowatt-hours a year. That system cost $7.5 million.

Jerry Daigle, senior project manager at the convention center, said the solar-power system was viewed back in 2009 as more than just a producer of clean energy for a county facility.

"If we don't do these technologies when they are new or emerging, then obviously we're never going to get the point where they are going to be economical," Daigle said.

kspear@tribune.com or 407-420-5026