IT will be "a couple of days" before the ESB can restore power to all homes affected by Storm Darwin.
Managing director of ESB networks Jerry O'Sullivan has described it as a ''mammoth task'' and ''truly epic.''
The ESB is currently assessing the scale of the challenge the staff faces.
''We hope to get to significant numbers today but to get to individual customers behind such damage will take a number of days particularly in our worst affected counties which is west Cork and Kerry,'' he told Morning Ireland on RTÉ Radio 1.
''Our major concern is that fallen lines and conductors are made safe so members of the public are safe,'' he said.
Crews have been moved to start in the worst affected areas in the south west.
''We need to travel to secondary, minor roads and right up farmer's lanes to get to our network and to get to our customers.
''We know from our damage assessments already that it is of a different order.
The managing director said he was anxious to make sure his crews got a couple of hours of sleep.
Up to 2,000 network technicians will tackle the huge task ahead after the ESB imported more workers from its sister company in northern Ireland.
''Our crews are going to cut their way in to our customers and that is going to take considerable time so we can get our heavy equipment escalators and JCBs in so we can erect new poles,'' he said.
''It's hurricane conditions we have encountered so it's a huge task ahead of us in the next number of days to try and restore our customers as quickly as possible,'' he said.
Helicopters are assisting the ESB in assessing the damage and its call centres are fully manned.
The company is dealing with more than 5,000 technical faults in fallen lines and conductors.
''It's a huge logistic operation but our people are good to go and have been fully in action since daylight,'' he said.