For solar power, scale is still a relative term. At its peak, the solar plant will be able to generate 75 megawatts of power, enough for about 11,000 homes. But that is dwarfed by the adjacent gas plant, which can produce about 3,800 megawatts of power. (A megawatt is enough to power a Wal-Mart store.)
Utilities are being pulled in different directions. They must ensure that the lights remain on at all times as well as provide the lowest-cost power to their customers. At the same time, they are being pressed to find ways to reduce their greenhouse gas emissions and invest in renewable power sources.
The latter is critical if the nation is to succeed in reducing its emissions of carbon dioxide. Power plants account for over a third of domestic greenhouse gas emissions that are responsible for global warming.
“We believe there is a cost to society associated with carbon emissions and not having energy security and not having domestic energy supplies,” Mr. Hay said. “But it’s not a level playing field for renewable versus fossil fuels right now.”
Mark Brownstein, an energy and grid specialist at the Environmental Defense Fund, praised FPL’s innovative thinking. “When we talk about getting to a low-carbon, clean-energy economy,” he said, “we know there is not going to be a single technology that is going to transform the industry.”
Currently, 29 states require utilities to increase the amount of power produced from renewable energy, which includes solar, wind, hydroelectric, geothermal and biomass. Last year, Congress considered a federal mandate for 25 percent of renewable power by 2025 as part of its energy and climate legislation. (The bill has since stalled.)
Utilities have been scrambling to meet the state requirements, and many will not be met, according to electrical utility experts.
While renewable power is growing, its share of the nation’s electrical generation remains small. Wind power, which has surged in recent years, accounts for less than 2 percent of the nation’s electrical output. Solar is even smaller. Coal, meanwhile, generates half of the nation’s electrical output, followed by natural gas and nuclear energy.
Part of the challenge in increasing the share of renewable energy sources is to make up for their variable nature — at night, for example, or when the wind does not blow. Because electricity cannot be stored easily, utilities must always produce enough power to meet electric demand at any given time. In practice, this means they need keep a lot of idle plants that can be fired up rapidly when demand spikes.
About 20 percent of the generation capacity overseen by PJM Interconnection, a regional transmission operator covering 13 northeastern and mid-Atlantic states, is used less than 100 hours a year, according to Lester B. Lave, a professor of economics at Carnegie Mellon’s school of business.
“As long as the contribution of wind and solar is very small, utilities can handle it very well,” Mr. Lave said. But what happens once the share of renewable power rises to 10 percent? Or 20 percent? “No one knows what the magic number is.”