California's Power Grid Hits 95% Renewable Energy. Sort of.

Something remarkable happened last weekend, according to a climate change newsletter by the Los Angeles Times.

California, the world's fifth-largest economy, hit nearly 95% renewable energy. Sort of...

There are several caveats. For one thing, Saturday's 94.5% figure — a record, as confirmed to me by the California Independent System Operator — was fleeting, lasting just four seconds. It was specific to the state's main power grid, which covers four-fifths of California but doesn't include Los Angeles, Sacramento and several other regions. It came at a time of year defined by abundant sunshine and relatively cool weather, meaning it's easier for renewable power to do the job traditionally done by fossil fuels.

And fossil fuels actually were doing part of the job — more than the 94.5% figure might suggest. California was producing enough clean power to supply nearly 95% of its in-state needs, but it was also burning a bunch of natural gas and exporting electricity to its Western neighbors. It's impossible to say exactly how much of the Golden State's own supply was coming from renewables.

That said, what happened on Saturday is definitely a big deal.... The 94.5% record may have been fleeting, but it wasn't some isolated spike. Most of Saturday afternoon, the renewables number topped 90%, with solar and wind farms doing the bulk of the work and geothermal, biomass and hydropower facilities making smaller contributions. Add in the Diablo Canyon nuclear plant — which isn't counted toward California's renewables mandate — and there was enough climate-friendly power at times Saturday to account for more than 100% of the state's electricity needs...

The important thing now is making sure the puzzle pieces of the grid fit together on hot summer evenings, like the ones last August when insufficient supplies after sundown led to rolling blackouts.

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