Updated from 4:36 p.m. EST

Sempra Energy ( SRE), having just completed a solar power plant near Las Vegas in December, is now working to increase the scale of the facility to become a major supplier of solar power to the consumer market.

If Sempra's plan works, it could provide the blueprint for commercial-scale solar power generation in the U.S.

The El Dorado Energy Solar facility, outside of Boulder City, Nev., is North America's largest and most cost-efficient thin-film solar power plant. The plant currently has 10 megawatts of electricity-generation capacity that can power 6,400 homes.

Sempra Energy's El Dorado Energy Solar facility in Nevada

The plant is powered by 167,000 solar panels manufactured by First Solar ( FSLR), based in Tempe, Ariz.

Sempra has a 20-year contract with a California subsidiary of PG&E ( PCG) to sell the power it generates from the El Dorado facility.

According to Sempra Energy, the thin-film technology it gets from First Solar uses "an advanced thin-film semiconductor technology to convert sunlight into electricity without air emissions or water use. These modules will generally produce more electricity under real-world conditions than conventional solar modules with similar power ratings."

The ability of First Solar's thin-film technology to generate power without using water or other liquids makes it ideal for deployment in arid ecosystems such as the southwestern U.S.

Sempra wants to add the next 40 megawatts of power capacity before the end of 2009. Sempra is calling the second phase of the project Copper Mountain Solar. However, Michael W. Allman, the CEO of Sempra Generation, says that there is a big difference between a 10-megawatt plant and a 50-megawatt plant.

"We took a risk and built the El Dorado plant before we had a buyer for the power," Allman said in a telephone interview. "The capital requirements of the next phase are too great for Sempra to assume all that risk in the next go-around."

The total capital requirement for the Copper Mountain expansion is expected to exceed $250 million.

Allman said that the two biggest roadblocks for new solar installations involve getting construction permits and permits to connect new plants to the power grid. Sempra's model aims to circumvent these issues by building plants on private land that are near existing energy infrastructure.

Sempra is hoping that the Copper Mountain expansion will benefit from federal loan guarantees from the U.S. Department of Energy.

"If we can get a federal loan guarantee, we can break ground on the Copper Mountain facility by the second quarter of 2009, and we could possibly start producing electricity before the end of the year," Allman said.

While Sempra hasn't yet inked a new deal with First Solar for the Copper Mountain expansion, Allman said that First Solar's panels are currently "the best solution."

"First Solar provides solar panels that, when deployed in a system, provide the lowest-cost solar electricity today," Allman said.

The partnership between Sempra Generation and First Solar has the potential to be a game-changer in the solar space, according to Morningstar equity analyst Mark Barnett. "Being the world's most efficient solar plant is certainly a milestone. If Sempra can use First Solar's technology to build more of these plants, it will put Sempra on the map as a major provider of solar power," Barnett said.

Shares of Sempra Energy closed down $1.10, or 2.8%, to $38.41 on Tuesday. First Solar shares closed up $6.47, or 6.2%, to $110.44.