In the studio's we leave everything running 24/7 for a number of reasons, but the most important are failures due to thermal cycling and inrush currents and the other of course is reduced setup time.
Biggest cost in a studio used to be the lights and the AC to keep the rest of the set from catching fire. The power for the cameras would be incidental, as those lights started at 1kW, and went up from there, and you might have had 15 or more on a set for general lighting, plus some spots that were used for fill in so the talent had a decent face shot without shadowing. With 30kW of light, and about the same for airconditioning to get the sensible heat out, who would notice a 2kW load for the cameras, and with a 5 hour or so warm up period before starting cal it would be just noise.
Just had some massmeters done, and took them to the lab the day before and plugged all in to warm up for 24 hours before the cal check, so they get stable.