Topaz Photovoltaic Solar Farm is a proposed 550 megawatt (MW) solar photovoltaic power plant, to be built by First Solar, Inc. in the Carrizo Plain, northwest of California Valley at a cost of over $1 billion. Pacific Gas and Electric announced an agreement to buy all the power from the solar power plant. Commenting on this project and a nearby 250 MW project announced at the same time, Daniel Kammen, the director of the Renewable and Appropriate Energy Laboratory at University of California, Berkeley, said "This scale is ten times larger than what was being talked about awhile ago".

OptiSolar, the instigator of the project, had optioned 9.5 square miles (25 km2) of ranchland, In November 2009, First Solar announced that it had purchased options to an additional 640 acres (260 ha) from Ausra's canceled Carrizo Energy Solar Farm. First Solar would reconfigure the project to minimize the use of land covered by the Williamson Act.

The Topaz Photovoltaic Solar Farm project would utilize thin-film PV panels designed and manufactured by First Solar. The project would deliver approximately 1,100 gigawatt-hours (GW·h) annually of renewable energy. The plant's power would be generated during the middle of the day, when demand for electricity — and price — is much higher than at night. The project is expected to begin construction in 2011 and be fully operational by 2014. California utilities are mandated to get 20% of their energy from renewable sources by 2010.

In late October 2010 the San Luis Obispo Department Planning and Building released a Draft Environmental Impact report for which is now accepting public comment.