Having looked at the graphs on the CAISO website, I think they had a supply problem and the New York Times is being a little disingenuous here. You can bring up

Having looked at the graphs on the CAISO website, I think they had a supply problem and the New York Times is being a little disingenuous here. You can bring up the renewables graph for the 14th here (change the date): http://www.caiso.com/TodaysOutlook/Pages/supply.aspx http://www.caiso.com/TodaysOutlook/Pages/supply.aspx At 6 PM, they had about 5.2 GW of solar still coming in. That rapidly and predictably dropped to zero over the next hour and a half. If my rough maths is correct that alone would be enough to wipe out almost the entire 12 percent operating reserve. There's also a really interesting graph of demand vs net demand minus solar and wind on the other page; you can see that total demand flattens out near the top, but net demand - which is what the grid operator has to find generating capacity to fill - continues to ramp up aggressively right up until the peak.