Long-term contingency plans should be drawn up to ensure essential services do not run out of electricity at peak times, the Economic and Social Research Institute (ESRI) has said.

In its quarterly economic review, which is published today, the ESRI says high growth in electricity demand and an aging plant portfolio have created a tight market for the next few years. While hospitals and large businesses are prioritised when supply is limited, simple services such as traffic signals can be cut from the grid at little or no notice, causing major disruptions. It is these aspects that need to be addressed, according to the ESRI.

When all plants are available, the probability of a shortage is very small, but the age and dilapidated state of some of the nation's main power generation plants, including Dublin's Poolbeg facility, mean that supplies can be cut at short notice. In November, 18 per cent of generation capacity was unavailable because of unplanned outages.

According to the ESRI, the generating units at Poolbeg, Tarbert and Great Island are essential for the reliability of the system and when all three are running the chance of a shortage is minimal. When none of the three is running, however, the probability of a shortage jumps to 47 per cent.

The ESRI also says the probability of a shortage is highest in the two weeks before Christmas. As a result the ESB, which currently has a monopoly on electricity generation in the Republic, said last month that contingency measures had been put in place, with approximately 300 megawatts of power on the North-South electricity interconnector being reserved for the Republic.

However, the ESRI believes that this isn't enough and that more should be done to ensure there is always a reserve supply to call on should the need arise. While wind can help in this area - during the last week in November and first week in December, 10 per cent of the State's electricity supply came from wind power - it is not considered a reliable source, as it is dependent on the weather.

Laura Malaguzzi, co-author of the report, says that power supplies need to be managed to ensure that supplies for essential services remain. She suggests more systems should be put in place to encourage people to switch off electrical appliances and lights when they aren't being used, and also puts forward the idea of charging higher prices for electricity used at peak times.

According to the ESRI, something needs to be done urgently to prevent this becoming a recurring issue every winter.