Police said the 15-year-old boy tossed one or two eggs over a fence at a Pennsylvania Electric Co. substation Monday night.
The combination of splattered egg and rain made the 34,000-watt transformers arc, creating a flash that was visible in most of Franklin, a town midway between Pittsburgh and Erie.
One witness reported seeing a fireball. Lights went out for a few minutes for at least 8,000 people in Franklin and in houses as far away as Oil City, five miles to the northeast, utility officials said.
The boy turned himself in and was treated at a hospital for ringing ears.