Depends on the generators in the system. Certain types of generators don't like / can't really / doesn't make sense to spin down much (e.g. nuclear, hydro). A

Depends on the generators in the system. Certain types of generators don't like / can't really / doesn't make sense to spin down much (e.g. nuclear, hydro). A nuclear reaction is going to generate as much heat as it does, you don't dial down a knob. A dam has (usually) a given amount of water flowing through based on external circumstances, not electric demand. Compare that with a coal generator, where you can just stop shoveling in more coal to reduce heat output. Sorta like that. I wouldn't really classify it as "bad for them", more like it's gonna be wasted anyways. Note: been a decade since I studied power systems, so... inaccuracies abound.