It is basically a very high spec thermos flask with a heating element in it so the power draw is fairly small. It's not like keeping a pan on the boil more, like a trickle charger topping up a full battery.
Definitely a case where I struggled as a non native speaker with the right choice of words.
Would be interesting to know how much energy it needs compared to always heating up from low temperatures.
Don't know him.
But constantly on the boil sounds, as tempting as the luxury would be, not very sensible.