California has broken more than one record for peak solar electricity production this month, and we don't even know by how much.
As we reported last month, California had a record 849 megawatts (MW) of solar power go into the transmission grid on June 8. That record is now old news: ON July 2, the state's utility-scale solar generators poured 965 MW into the grid, nearly 3% of the power California was consuming at the time. That record didn't last long: On July 6, 971 MW of solar came into the grid in the early afternoon.
That figure includes only solar power generated in large plants whose output is regulated by the CaISO. As Clean Energy Authority reports, the figure doesn't include most of the power produced on California's millions of rooftops. As CaISO spokesman Steven Greenlee told Clean Energy Authority, "We don't see residential. It's behind the meter."
Rooftop solar (both residential and commercial) that's "behind the meter" is generally counted as reduced demand for electricity rather than power put into the grid. Under California's net metering law -- recently expanded by the state's Public Utilities Commission -- rooftop solar energy that isn't used on site does get fed into the distribution grid, running the customer's electric meter backwards, but that's accounted for as demand reduction rather than power production.
With the recent boom in installation, it can be hard to find complete figures on how much rooftop solar capacity is out there. But according to Go Solar's California Solar Statistics site, Pacific Gas and Electric, Southern California Edison, and the California Center for Sustainable Energy administer net metering agreements with 862 MW worth of rooftop solar capacity between them. Overall, the California Public Utilities Commission estimates the state has a total rooftop solar capacity of 1,255 megawatts. If even half of that was producing power on July 6, California's solar output could well have peaked significantly above the 971 MW CaISO can track.
So we've definitely set a record, with more likely to come as summer heats up and more facilities, large and small, come online. Perhaps soon we'll even be able to track just what those records really are.