MORE than a quarter of homes will lose power during peak periods in the event of an ESB strike, despite strong contingency plans being put in place to ease the pain.
As the December 16 deadline for industrial action at the semi-state looms, retailers warned of having to lay off staff while travellers face major disruption if the lights go out.
Court cases would also be severely affected, with most criminal matters likely to be delayed until the New Year.
The Criminal Courts of Justice (CCJ) building in Dublin has ancillary power, but outside the capital there would be massive disruption.
A plan has been drawn up by regulators and the national grid operator to lessen the impact on homes and businesses, but many families will still be without power for hours at a time.
The Irish Independent has learned that at any one time more than 500,000 homes – or one in four countrywide – would be cut off for up to three hours during the evening peak when demand is highest. However, the cut-offs will be staggered across the country to help "share the pain", industry sources said.
National grid operator EirGrid will use electricity generated by independent suppliers, wind energy and imports from Northern Ireland and the UK to power homes and businesses.
However, there will be a shortfall – which will result in some properties being cut off.
ESB chief executive Pat O'Doherty yesterday refused to answer questions about the impact of the threatened blackout, saying it would be unhelpful to do so during talks.
The deadline is now just 11 days away and will affect customers in the middle of the busy Christmas shopping period.
The notice period expires at 8am on Monday, December 16, unless management and staff hammer out an agreement aimed at resolving a row over a €1.6bn deficit in the staff pension scheme.
Talks between union officials and ESB executives ended without agreement last week, with both sides acknowledging that a wide gulf persists. Notice of industrial action was served last Friday.
If strike action goes ahead, automatic railway level crossings will have to be manned to prevent accidents, the Dublin Port Tunnel will be shut putting thousands of HGVs on the streets of the capital and criminal cases in courts outside Dublin will have to be adjourned.
While essential public services including hospitals, garda stations, fire stations and key government departments will be powered at all times, homeowners and businesses will take the brunt of the hit.
Major employers including Largo Foods, which produces Tayto in Ashbourne, Co Meath, said that staff in some plants would have to be sent home because they couldn't work in a building without power for health and safety reasons.
However, the Commission for Energy Regulation (CER) and national grid operator EirGrid have drawn up plans to keep power flowing as much as possible in the event of ESB workers downing tools.
"We are closely monitoring this," a CER spokesman said. "There are emergency plans in place and we do meet with stakeholders. We met EirGrid and the Department of Energy recently."
It is understood the talks centred on so-called "load shedding" – where power is shut down to parts of the grid because demand exceeds available supply.
While the ESB produces about half the country's power from its power generation assets, EirGrid has access to nine independent generators across the country.
These can provide about 2,800MW of energy, enough for about 2.8 million homes, when operating at peak.
It can also import a further 200MW from Northern Ireland, and 500MW through the East-West interconnector, a high-voltage power line that runs to Wales from Rush, Co Dublin.
Wind energy can also be used to power homes – record peaks show that 50pc of our power has come from wind, and about 17pc is routinely delivered on a daily basis.
While peak demand runs to about 5,000MW per day, at least 3,500MW could be produced from conventional sources. The remainder will come from wind, but there is likely to be some shortfall, resulting in shut-offs.
"With a really windy day, you might avoid any load shedding," one source said. "Maybe 25pc of homes might be disconnected, but the sense is to share the pain. Nineteen large-scale customers are connected to the grid. Load shedding tends to be confined to residential and not commerce or industry."
The shut-offs would be staggered, meaning that homes in a given area would be disconnected for a number of hours, but once power was restored they would be placed at the bottom of the queue before being disconnected a second time.
The shut-offs would be spread geographically across the country, so there were no peaks in demand in particular areas.
Despite ESB Group of Unions general secretary Brendan Ogle previously boasting that his members controlled the electricity network, as much power as is available will continue to flow to homes.
This is because EirGrid – which is entirely separate from the ESB – sends the power to about 100 points across the network, where it is distributed to homes and businesses in a largely automatic process.
Sources said the strike would have "no impact" on power supply to homes, and that ESB Networks was likely to provide emergency services, for example if a line goes down, meaning power will flow uninterrupted. The plans have been in train for the past number of weeks.
Retail Ireland called for unions to call off the threatened strike, warning that many smaller shops would be forced to immediately close and send workers home, meaning employers and staff would bear the financial loss.
Education Minister Ruairi Quinn said he was sure that all that could be done, was being done.
"I'm sure that's what they are trying to do but I'm not going to comment because I don't want to make the situation any more difficult than it actually is," he said.
"I just hope that those talks proceed satisfactorily."
Paul Melia and Luke Byrne