Good point, but one small nitpick. Combined-cycle plants are optimized for efficiency, at the expense of ramp speed, so they are not really used as peakers. Gas turbine plants are what you are thinking of; basically, a jet engine with a generator attached. Right on for the rest.
Apologies I wasn't clear. When I say CCGT can throttle quickly, I compare it to coal and nuclear ("legacy thermal", if you will), not peakers that can ramp in minutes from 0-250MW of output. Appreciate the call out on my ambiguity.
Everything I've read about the duck curve in California and how ISO manages it has indicated that CCGTs are ramping "fast" (~13GW in 3 hours [1]), but I suppose it's all relative.
