I would think just electrical would be ok, isn'y your add in a section where everyone is a electrical contractor? like right after electric companies (utilities) and before electric service and supplies etc. seems to me you might of wasted letters even saying what you did, like joe joe's Electric (or whatever)and what you specialize in, name and numbers, maybe logo would be enough, the fact that you a electrical contractor should allready be estabished by the section of the book your in.