Some 11,000 buildings in Dublin city centre briefly lost power on Friday afternoon.
A fault on a power line at Heuston Station affected people on both sides of the River Liffey.
These were mostly in the Stoneybatter and Kilmainham areas of the city.
Other areas such as St Stephen's Green and Rialto were also affected.
ESB crews put a temporary fix in place within five minutes.
They are now working to find a permanent solution.
The ESB has apologised for the loss of supply.
While Irish Rail services appear to be unaffected.