NIE says around 21,000 customers are without electricity across NI, after power was restored to 24,000 amid Storm Ophelia.
However the number of homes affected is expected to rise as strong winds gusting from 60mph to 70 mph continue to sweep the region.
Sara McClintock from the company said: "NIE Networks staff are continuing to respond to faults as they arise on the electricity network.
"We will be working into the night to do all that we can to restore electricity supplies to our customers as quickly and safely as we can."
Customers should call 03457 643 643 to report faults.