The California Independent System Operator or CAL-ISO reports solar production went above the one-gigawatt level twice in the last month.  Cal-ISO's Stephanie McCorkle says solar's contribution to the power supply was especially helpful in mid-and-late-August.  That's when the grid experienced its highest demand all year, "The thing that is really nice about solar power is that it actually peaks at the same time that our air conditioning demand peaks in California and that's in the late afternoon hours."

McCorkle says wind power is still the cheapest in the green energy sector, but solar is in much greater supply and the costs of production are coming down.