Grid Alerts Explained

SONI is responsible for the safe and secure operation of Northern Ireland’s electricity system. Northern Ireland’s energy demands are monitored by SONI’s Control Centre which carefully balances supply and demand on a minute-by-minute basis. We manage the supply of electricity in real time, from electricity generators in Northern Ireland, as well as generators in the Republic of Ireland and through a subsea interconnector with Great Britain. This involves the movement of large volumes of electricity around Northern Ireland, where it is then supplied to large energy users, and to homes and businesses via NIE Networks.


An alert is not an unusual event. When the buffer between electricity supply and demand is tighter than SONI would like, SONI issues an alert to the electricity sector. Alerts are more likely to take place in the winter months when demand for electricity is at its highest. A System Alert (previously known as an Amber Alert) is the lowest level alert, followed by System Emergency (previously known as a Red Alert).

When SONI issues a System Alert there is no immediate impact for users of electricity. Instead, a System Alert warns of the potential for temporary electricity supply issues in the near future, so that our expert engineers and those across the electricity sector can take pre-planned actions to protect the integrity of the grid. It is a signal for all generators of electricity to make their power plants available for use and not to put their power plants at any risk of tripping. A System Alert often passes off without incident once a sufficient buffer between electricity supply and demand is restored.

A System Emergency State is much less frequent than a System Alert. It is issued by SONI when there is a high risk that not all electricity demand can be met. When the power system is in this state, SONI engineers will work closely with NIE Networks engineers to take pre-planned actions to protect the integrity of the grid. These actions may include implementing planned emergency power cuts for some users. A System Emergency is lifted once a balance between electricity supply and demand is restored.

In the unlikely event of a System Emergency, to protect the integrity of the power system and prevent a more serious event, planned emergency power cuts may have to be implemented by SONI and our partners NIE Networks. Some customers may experience temporary planned emergency power cuts. By doing this we remain in control of the grid and avoid the risk of extensive unplanned interruptions of electricity supply. In such situations, SONI and NIE Networks will work to make planned emergency power cuts as short-lived as possible and will rotate the locations that are impacted by them. If you think you are
experiencing a planned emergency power cut, please visit for up-to-date information.

Planned emergency power cuts are a measure of last resort, put into operation when circumstances require our specialist engineers to take action to protect the integrity of the power system during a System Emergency State. In this scenario, deliberate measures are taken to interrupt power supply to a portion of electricity users, for a period of time, to reduce electricity use when the supply of electricity is inadequate. Plans, approved by the Utility Regulator, are in place to undertake such planned emergency power cuts, while protecting the supply of electricity to identified critical infrastructure.

A blackout occurs when there are electricity power cuts across a widespread area in an uncontrolled manner. One of the reasons that planned emergency power cuts are put into operation is to avoid widespread blackouts. Plans, approved by the Utility Regulator, are in place to undertake the restoration of supply to customers after a System Blackout State, in the unlikely event of this occurring.


On occasion, the buffer or margin between supply and demand can be smaller than we would like, this could be due to a fault or planned outage at a power plant or if the wind isn’t blowing on a cold dark winter’s day. We are not an outlier here – National Grid in GB, EirGrid in the Republic of Ireland and electricity system operators in Europe are all experiencing similar challenges as we move through the transition from systems reliant on fossil fuels to cleaner systems based on renewable energy.

This year’s winter outlook, an annual document produced by SONI, stated that there is little risk of planned emergency power cuts in Northern Ireland. Northern Ireland will not undertake a planned emergency power cut to facilitate security of electricity supply in the Republic of Ireland.


SONI studies suggest that the risk of the system entering the Emergency State, due to insufficient generation being available to meet the demand, is low. Nonetheless, SONI has thoroughly planned for grid alerts, and is working with the Utility Regulator, the Department for the Economy, NIE Networks, EirGrid, the National Grid(GB) and large energy users, to reduce the impact of alerts for all electricity users.