Yet another half-gigawattsolarpower project is coming on-line in California.

Late last year, the 550-megawatt capacity Topaz Solar project achieved full commercial operation and claimed the title of largest solar plant on-line in the world.

And now Topaz has to share the crown with First Solar's 550-megawatt Desert Sunlight project in Riverside, Calif., which went all-on this month, according to the California Independent System Operator (CAISO) website.

The projects use approximately 9 million solar panels each.

Desert Sunlight is co-owned by NextEra Energy Resources, GE Energy Financial Services, and Sumitomo Corporation of America, and is constructed on land managed by the federal Bureau of Land Management. In 2011, the U.S. DOE issued loan guarantees of $1.46 billion for Desert Sunlight.

Topaz has 9 million solar panels across 7.3 square miles in San Luis Obispo County on California's Carrizo Plain. The solar farm was not the recipient of a loan guarantee and is built on disturbed farm land miles away from sensitive areas in the Carrizo Plain National Monument. PG&E will purchase the electricity from the Topaz project under a power-purchase agreement. Followers of ancient history will recall that this project was originated by OptiSolar and that some of the Topaz real estate was once intended for an Ausra CSP solar power plant.

But these two projects from First Solar will soon yield their glory to SunPower's 579-megawatt solar project in Antelope Valley, Calif., which is scheduled to go fully operational in the first half of this year and claim the title of the largest operational solar project on the planet.

Manufacturers of the world's most efficient solar panels (SunPower) and some of the world's less efficient panels (First Solar) are still able to make large solar projects work, revealing that panel efficiency is less important than project economics and execution in 2015.

Information on these interconnections comes courtesy of the WECC website, CAISO's Master Control Area Generating Capability List and the intrepid sleuthing of GTM solar analyst Cory Honeyman.

Here's a chart showing the top three U.S. PV power plants under development in the U.S. 

Project Name Developer Capacity (MWac) Capacity On-Line State Offtaker Owner
Topaz Solar Farm First Solar 550 550 CA PG&E MidAmerican Energy Holdings
Desert Sunlight First Solar 550 550 CA PG&E, SCE NextEra Energy Resources, GE Energy Financial Services, Sumitomo
Solar Star  SunPower  579  412.5  CA  SCE MidAmerican Energy Holdings

Source:  GTM Research's Utility PV Market Tracker

Check out the GTM Research Utility PV Market Tracker for much more information on utility-scale solar deployment in the U.S.