ESB Networks has said that nearly 1,000 customers are without electricity in Slane in Co Meath.
Power was not expected to be restored before 1.15am at the earliest.
It is believed 991 customers are affected.
Gardaí have said that traffic lights in Slane are out of order as a result of the power outage.
They asked motorists to be careful, particularly on Slane Bridge.
