ESB technicians are trying to restore power to almost 20,000 customers in Dublin this morning.
The outage, caused by a fire, has left several residential neighbourhoods in the dark - especially in the Mount Merrion, Stillorgan and Rathfarnham areas.
Repair crews have said service should return by around 8am or 9am.
Meanwhile, in Limerick 130 customers will be without power until this afternoon.
A fault in the Abbeyfeale area should be fixed by around 2pm.
Another fault in Belmullet in Mayo should be fixed within the next couple of hours to get over 200 customers back on the grid.