Apparently one of the nuclear turbines went offline because the turbine was exposed to the open air (for cooling during the summer) and some of the sensors triggered a shutoff of the turbine when they detected unexpected temperatures.

Another case where systems misbehave when they’re exposed to circumstances outside the expected range.

I think it's fair to say that their top two energy sources are natural gas and coal, although "mostly natural gas and nuclear" would also be fair, in its own way.

https://www.utilitydive.com/user_media/diveimage/ercotmix.pn...

Nuclear relies on water for cooling, which froze in at least one plant.