OG&E spokesman Brian Alford was quoted by Reuters as saying, "We have a mix of outages on our system and are beginning the assessment process to determine the full extent of the damage to our transmission and distribution system."
The tornado with winds speed of about 200 miles per hour destroyed two elementary schools and a hospital in Moore, south of the city.
OG&E, which is seeking help from outside utilities to restore power in the area, said about 38,000 of its customers were without power in Oklahoma city.
About 51 people including around 20 children have been reportedly killed in the devastating tornado.
Oklahoma Governor Mary Fallin was quoted by the BBC as saying that it was a tragic day.
