More than 1,500 properties in Abertridwr and Senghenydd were without power because of an underground cable fault.
Western Power Distribution said they were able to switch supply circuits to restore power to all but 330 properties within an hour of the fault, which happened at around 12.40pm today, Friday January 22.
A spokeswoman for the firm said engineers were working to restore electricity to the remaining homes by 4pm with the use of temporary generators while the fault is found.