As far as I know, the 1V draws hardly any power when it's to hold the shutter open on bulb exposures. From that I extrapolate that hardly any power is used while the camera is just sitting there with it's shutter closed.

The manual states, "When the camera is not to be used, set the (camera to off). This will prevent accidental battery drainage if the shutter button is held down inadvertently."

So, I would say that the camera uses effectively no power while just sitting there, on or off. Film advance will certainly use some power, as will shutter activation, focusing, and metering. Lenses with IS will presumably use more.