I just watched episode 13 of season 2, "Prototype", and I noticed a reference, whether intentional or not, that I thought was pretty cool. Right before Prototype 0001 wakes up, Torres says, " I'm going to try adjusting the flux capacitance." It's a time-traveling robot!!!!!
A similar reference occurs in TNG: Hollow Pursuits. Barclay's scripted line included the words "flow capacitor", but Dwight Schultz says "flux capacitor", either by accident or design.
I always thought it was utterly hilarious that Kirk and company stole Christopher Lloyd's Bird of Prey, then used it to time travel. "Once this baby hits warp 8.8 you're gonna see some serious shit."
No doubt it was used to handle enormous amounts of energy and not just electricity and do it efficiently. I suppose the flux characteristic handled high energy warp plasma. The capacitor itself must have been very small. There was nothing said about time travel.