Here is a power transformer on my street, operated by Energy United, one of the two power companies in the area. (The other is Duke Power. I’d have to say that having their own nuclear reactor probably gives Duke some sort of competitive edge.)
This sign (larger image) gets right down to business, no subtlety here: “Can shock, burn, or cause death.” I love the illustration. It’s as if the box itself were attacking the stick figure human, hurling out lightning bolts from its innards.
On the Deadly Suburban Danger Sign Scale, this sign ranks high. Bonus Points for the ecumenical name, Energy United. Sounds a bit like some sort of European Football Club.