Supply usage of Afterburners, Shields & Regenerators

I've been wandering - how do Shield Regenerators use supplies? As in, if it says "Supply Usage = 10" in the components.txt data file, does that mean it'd cost 10 to regenerate the shields from 0->100%? Or is it not implemented at all?

For that matter, what would happen if regular Shield Generators were given a "Supply Usage > 0"? What about Afterburners? Do they use their Supply cost just at the start of combat?