Potential for power system alerts this winter lower than last year, says EirGrid

Risk of amber warnings ‘most likely during the coming winter peak hours and at times of low wind and low interconnector imports’

There is a lower risk of power system alerts in coming months compared to what was anticipated last year though the balance between supply and demand remains tight, according to EirGrid’s winter outlook report.

The report, issued on Monday, helps to inform the electricity industry and supports preparation for the period from October 30th to March 31st, 2024.

The improved outlook compared to last winter is due largely to the work on the State-led security of supply programme, which will have a positive impact on generation capacity and deliver an expected 270 megawatts (MW) of temporary emergency generation this year, EirGrid said.

Further capacity of temporary emergency generation, of 380MW, and other capacity including batteries will be delivered in 2024. The UK, which provides power if needed to the Irish grid via two interconnectors, is also more positive in terms of outlook and arrangements are in place with large energy users including data centres who will support the system in the event of unforeseen challenges with generation capacity.


As the transmission service operator for Ireland, EirGrid studies expected generation capacity and forecast electricity demand to determine if there is adequate generation capacity margin on the grid.

The winter outlook identifies periods where the margin between generation capacity and forecast peak demand is low and security of supply of the electricity system may be at risk.

The outlook uses a metric called the loss of load expectation (Lole) — the number of hours in a period, typically a year, during which the available generation of a plant will be inadequate to meet the demand.

The Commission for the Regulation of Utilities, sets the Lole standard at eight hours per year. The Lole for the coming winter is 21 hours . It is a point-in-time assessment, based on the best information available in September — and is subject to change. It was 51 hours for the winter of 2022-2023.

There is a risk that the system will enter “alert [amber] state” at times, most likely during the coming winter peak hours and at times of low wind and low interconnector imports. The outlook concludes “there is a reasonable probability of the system entering the emergency state (red) at times, due to insufficient generation being available to meet the demand”.

Emergency protocols are in place with large energy users where sufficient notice of an event can be provided — a minimum of one hour. This along with increasing capacity, including temporary emergency generation should be able to mitigate the impact on homes and businesses, according to EirGrid.

Budget 2024: What it means for households and businesses

Listen | 37:33

Growth of demand from large energy users (mostly data centres) has been 99MW in the year to date.

“It is encouraging to see that the risk of disruption to electricity supplies due to insufficient generation has reduced for this winter. It is worth noting that there were no system alerts last winter when the risk of going into alert was significantly higher than it is this winter,” said EirGrid chief executive Mark Foley.

“The margin between supply and demand this winter may be tight at times particularly over the 5-7 pm evening peak. However, this winter, we do have more capacity becoming available to us over the coming months. This includes the temporary emergency generation units that will gradually become available to us from next month. This is an insurance policy that will only be used if required to secure electricity supply.”

In addition to additional capacity, emergency protocols were in place with large energy users that will see them reduce demand by up to 75 per cent “should we enter a system emergency state”, Mr Foley noted.

A total of 240MW in emergency generation capacity is coming on stream. Energia’s site at Huntstown, Co Dublin, is due to be available from early December, while a temporary plant on ESB property at North Wall in Dublin is due to be available from the end of this month. Both are gas-fired.

Diesel-fired plants at Shannonbridge, Co Offaly, and Tarbert, Co Kerry, will be available from December and over the winter of 2024-2025 respectively. They will only be used when it is clear that market-sourced generation will not be sufficient to meet system needs.

Kevin O'Sullivan

Kevin O'Sullivan

Kevin O'Sullivan is Environment and Science Editor and former editor of The Irish Times