The Electric Possessor Ghosts are minions of the electric spectre Killerwatt. As their name implies, they can possess equipment that runs on electricity.
The Ghostbusters first encounter Electric Possessor Ghosts possessing a Stacy's Department Store building and its electrical appliances. All of the spirits, a little over a dozen, present were captured and put into the Containment Unit. However, the Ghostbusters didn't know that the paranormal event was bigger than they thought it was until the Containment Unit shut off. The backup generator kicked in, but it was possessed by one of the electric ghosts and then ran away. Knowing the danger of the situation, the Ghostbusters had to resort to old-fashioned methods to keep the Containment Unit working.
After the team traced the psychic turbulence from power lines, they found a power plant in Brooklyn was the source of the electric ghosts. After meeting Killerwatt, the Ghostbusters witnessed the possession of Ecto-1. After the team finally confronted and trapped Killerwatt, the remaining ghosts disappeared.
Possession: As stated above, the Electric Possessor Ghosts can possess anything that runs on electricity. They seem to not be completely limited by what they possess as many of the objects could fly while under possessor will.
Flight: Standard ghost power.