An ESB repair crew had to travel by helicopter to Cape Clear Island, which was without power and water since early yesterday.
Cape Clear is just three miles long by one mile wide and lies eight miles off the coast of West Cork
The island ferry was unable to collect the crew from the mainland because the island's storm gates could not be opened to let the ferry out.
The gates, which have been operational since last summer, are powered by electricity and would normally open in under one minute.
A back-up system also failed. It could not be used because of the continuing high swell at sea.
Power was restored on the island around 30 minutes after the arrival of the ESB repair crew.
Máirtin Ó Méalóid of the Island's Development Co-op says islanders are delighted with the new storm gates but what has happened has highlighted just how inadequate the back-up system is.