I also think there is a possibility that some standing flows for smaller ter'angreal may have been discrete flows that have been tied off in a localized area. So instead of a physical battery powering your flashlight, for example, you'd have tied off flows that would generate power when a certain movement set off a conditioned flow (currently known as wards). Instead of a switch, gesturing in a certain way would cause the flows to behave a certain way.

I'm imagining a non-channeler in the Age of Legends entering a room, clapping his hands to turn on the lights, maybe making an upper or downward movement with one hand to modify how bright the lights were and then snapping a finger to set his couch to recline.

We know, for example, that tied off flows would last indefinitely unless the channeler specifically set an expiration date, so it seems that the standing flows for smaller objects and effects could be very discrete and on their own sub-level power system, while a larger use, such as powering an entire city's electric grid would be on a different and far larger scale.