News and analysis about renewable energy in California.

California On Track for Gigawatt of Solar Grid Power This Summer

Solar panels on a schoolhouse roof | Photo: Matt Montagne/Flickr/Creative Commons License

The California Independent System Operator (CaISO), the agency that operates the power grid in California, reported last week that the state hit a new record for solar power feeding into the grid: on Tuesday July 24, the contribution that solar electricity made to the state's power grid reached a record 978 megawatts. That replaced a record set earlier in July, which bested June's record.

Those figures don't include much rooftop solar, which doesn't feed into CaISO's grid. But the numbers are sure to continue rising as more grid-tied solar panels come online. According to ReWire's calculations, it's very likely that California will set a 1,000 megawatt record for solar grid power before the end of this summer.

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What is...? The Grid
CaISO provides hourly figures on the amount of each form of renewable energy entering the state's power grid. The figure for solar energy generally peaks each afternoon between noon and 3:00 p.m., when the sun tends to shine most strongly.


The day-to-day solar grid power peaks can vary wildly, depending on the weather, maintenance and repair activities on larger solar installations, and demand for power -- CaISO will ramp down production if we aren't using much electricity. There's also a weekly cycle: power consumption tends to drop on weekends.

Because of this daily variability, it can be hard to discern trends within the noise. But according to CaISO's figures, the typical peak solar grid contribution surpassed 800 megawatts on June 8, and then broke the 900 megawatt barrier on the first day of July.

To smooth out the noise in CaISO's daily solar peak figures, ReWire took each date in June and July and charted the average peak output of the previous five days, which statisticians refer to as the five-day moving average. This helps make trends over time clearer, and according to our calculations the state's peak solar output is very likely to surpass 1,000 megawatts -- one gigawatt -- during August or September. Click to view this rough chart at full size:

CaISO-solar-capacity-graph-7-30-12.png

Despite a significant dip in mid-July, the upward trend is notable. Of course two months' data isn't enough to establish long-term trends, but in the context of rapid installation of solar capacity in the state and last week's record just 22 megawatts shy of the 1,000 megawatt mark, August or September seem a reasonable estimate of when we'll surpass that mark.

Prognostication is risky business, and several obstacles remain to hitting 1,000 megawatts. The days are getting shorter, for one thing: the state is likelier to experience cloudy weather as summer winds down and there's always a chance that large installations will go offline for maintenance, repair, or other unanticipated events.

But as more and more large property owners install solar generating capacity, even cloudy winter days will cease to prove much of an obstacle. Germany, which has a climate comparable to that of Seattle, put 22 gigawatts of power into its grid in May, the result of strong government support for photovoltaic power. In other words, even when we do break the gigawatt barrier, we have lots more room for improvement. A gigawatt is about a fortieth of California's typical peak power demand: a very large drop in a gigantic bucket.

ReWire is dedicated to covering renewable energy in California. Keep in touch by liking us on Facebook, and help shape our editorial direction by taking this quick survey here.

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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