A veteran analyst has calculated that the facility can produce power at a cost of 7.5 cents a kilowatt-hour, less than the 9-cent benchmark for conventional electricity.
If that's so, it marks a milestone that advocates for renewable energy have longed for: "grid parity," in which electricity from the sun, wind or other green sources can meet or beat the price performance of carbon-based fuels.
"We now have an alternative-energy source that can actually deliver cost-competitive electricity with no subsidies," said Mark Bachman, senior equity analyst for Pacific Crest Securities in Portland, Ore.
The stock of First Solar Inc., the Tempe, Ariz., company that manufactured the solar modules for the project, has soared about 20 percent since Bachman released his analysis in mid-December.
The trouble is that no one involved in the deal is willing to confirm Bachman's conclusions, not wanting to reveal valuable know-how.
What they will say is that this facility, known as El Dorado Energy Solar, is producing electricity at costs below anything comparable to date.
"Our contract is the least expensive solar power ever delivered in the world at scale," said Michael Allman, chief executive of Sempra Generation.
Sempra constructed the project on 80 acres next to its El Dorado Energy gas-fired power plant, about 40 miles southeast of Las Vegas in Boulder City, Nev. The solar facility uses photovoltaic panels similar to those mounted on homeowners' roofs, except the panels are anchored to the desert floor in long rows and there are lots of them — 167,000, to be exact.
Another difference is technology. Conventional solar modules turn sunlight into electricity using a semiconductor known as polycrystalline silicon. That's the same material used in computer chips. Until recently, it had been pricey and in short supply.
First Solar uses a lower-cost semiconductor known as cadmium telluride, which it fashions into thin-film cells that are cheaper to manufacture than their silicon-based counterparts.
"It's like the Wal-Mart of solar panels," Allman said.
Some energy wonks are likely to dispute Bachman's conclusion that the El Dorado project has achieved grid parity. Many focus on the per-watt installation cost of such systems.
What's clear is that the costs of solar power are dropping dramatically across the industry as the technology is more widely adopted and producers become more efficient.
First Solar Chief Executive Michael J. Ahearn said his company had cut the cost of manufacturing its modules by 67 percent over the past four years.
"The photovoltaic industry," Ahearn said, "is much closer to generating affordable solar power than most people realize."