every metal atom requires two electrons (or three for some metals), and you typically need 1–3 volts, and sometimes there are side reactions that waste most of your electrons; probably 'faradaic efficiency' or 'coulombic efficiency' is the term to google

slm and ded and metal paste deposition just have to rearrange some crystal structures; in electrolysis (including ecm machining) and electrodeposition you have to actually rip molecules apart, atom by atom and electron by electron

basically you're charging a battery, so you can get a rough idea by thinking about how much energy a battery could store if it was the same size as your desired workpiece