NIE Networks said a total of 4,000 households and businesses were cut off at one stage on Saturday, but power was restored to more than 3,000 of them by Saturday night.
The remaining 900 had power restored by 01:00 GMT on Sunday.
The company said the cut was caused by faults in an overhead line and an underground cable.
Power has been restored to the remaining 900 customers without electricity in Comber, County Down.