I think I found it all, so I’m putting it where I can find it later. Maybe others will benefit from my efforts.
Potentially lethal electricity is burning damage with either Surge, +20% (B105; Powers, page 102) or Arcing Surge, +100% (Power-Ups 4 Enhancements, page 21). The difference is that conductive armor is reduced to DR 1 against Arcing Surge. With either enhancment, any target with the Electrical disadvantage (B134; electronic equipment without a character sheet has this) that takes over 1/3hp must roll HT or be disabled for one second per point of failure (until repaired on a critical failure). Repairs are described on B484.
But wait, there’s more. On B432-3, we learn that localized electrical attacks include Side Effect (Stun), +50% (B109, B35), and, if such an attack injures a hand or arm, the target must make a Will roll or drop whatever is being held in that hand, +?% (B???). Full-body electrical attacks add Side Effect (Unconsciousness, Attribute Penalty, -2 DX and Secondary Heart Attack), +330% (B109, B35). For bonus points, explain to me whether or not the effects in this paragraph are supposed to be included for free with Surge/Arcing Surge.