work on the principle that the power supply for most 3d printers is somewhere between 100-300 watts.
I've rarely seen anything over 350 watt listed in a speification.
So the printer can't pull more than that and usually it uses a lot less.

Once an extruder and hotbed are up to temp then the power draw drops considerably as maintaining that temperature costs less power than heating cold metal up to it fairly quickly.

They are certainly draw a LOT less power than an electric oven.