The Republic used enough electricity to power more than five million households during a record peak in demand last year.

Eirgrid, the State agency that operates the electricity transmission system, said yesterday demand in the Republic hit 5,035 megawatts (mw) for a time on Tuesday, December 19th, 2006.

This means that the market required enough energy to power more than five million homes at that point. Eirgrid, which published its annual report yesterday, said this was a record.

There are fewer than two million homes in the Republic and they account for less than half the market. Industries, businesses and large organisations take up most of the demand. Overall demand for power grew 4.48 per cent last year.

Eirgrid chief executive Dermot Byrne said the system was able to meet the demand with enough capacity in reserve to deal with the loss of any major power generator.

However, he states in the annual report that there was less electricity generating capacity available than expected last year.

There is a total of 5,836mw available from power plants and other sources. At the launch of the report yesterday, Mr Byrne said that on average, power plants were available 78 per cent of the time, which he said was satisfactory.

He added that 80 per cent-plus availability would be ideal and pointed out that 88 per cent was "best practice".

Eirgrid chairwoman Bernie Gray said that the ESB plan to shut down four plants by 2010 should not result in power cuts. The plants have a total capacity to produce 1,300mw of electricity.

Three new facilities with a total capacity of 1,200mw are due to come on line between now and 2011. But demand is expected to grow by 3 per cent a year over the same period.

This has led ESB unions to warn that there could be power shortages if the closures go ahead.