Skip to main content

Emergency Power Cuts

Planned Emergency Power Cuts

Planned Emergency Power Cuts are a form of emergency power cut which is used by energy companies in response to severe shortage of electricity generation in Northern Ireland.

Planned Emergency Power Cuts are used to reduce electricity consumption by switching off the power supply to groups of customers. It is a last resort method of protecting electricity supply when the entire system is at risk.

It is only used in rare, exceptional circumstances but is recognised globally as a standard method of balancing electricity supply and demand.

Find Out Your Block Letter

In the event of a planned emergency power cut, different block letters are timetabled to be without power for around three hours once a day. To find out your block letter use our block map at the link below.

Block Map

Read more about Planned Emergency Power Cuts in the following Frequently Asked Questions.

What's Happening?

  • What is a planned emergency power cut?

    Planned Emergency power cuts mean switching power off to at least 5% of NI households at once.
    The System Operator for Northern Ireland (SONI) works to ensure the electricity supplied (by generators such as power stations, renewable energy sources and interconnectors) is balanced with the customer demand.
    If there is not sufficient supply, the balance of the electricity system is at risk. 
    To restore the balance SONI instruct NIE Networks to reduce demand for a period of time by removing customers off the network – this is referred to as Planned Emergency Power Cuts.
    It is important to note that Planned Emergency Power Cuts are different to planned local outages, such as for maintenance, and unplanned outages caused by damage to wires and cables, for example during storms.

  • How do planned emergency power cuts work?
    The electricity system in Northern Ireland is sectioned into blocks that can be temporarily switched on and off, typically for three-hour periods, until the shortage is resolved, and the network can safely go back to normal.
    Each electricity meter is assigned a ‘block letter’. In the event of a planned emergency power cut, where there is time to implement an emergency rota, different block letters will be timetabled to be without power for around three hours once or twice a day.  Visit our Block Map to find out what block your postcode is. 
    NIE Networks has a plan for Planned Emergency Power Cuts, including a schedule or a “rota” for the sequence in which planned emergency power cuts happen.
    The plans are drawn up by specialist engineers within NIE Networks and implemented immediately when instructed.
    This plan seeks to spread the inconvenience equitably: a limited disruption to many, rather than more significant disruption to a smaller number of customers.
  • How much notice will be given?

    Planned Emergency Power Cuts can take place without warning, if SONI instructs NIE Networks to reduce demand immediately to protect the electricity system/network and avert longer term issues.  However, the aim would be to notify customers via media and social media channels before a planned emergency power cut is undertaken.

  • Why would emergency power cuts happen?

    If there isn’t enough electricity being generated to power every home and business in Northern Ireland at the same time, SONI – who is responsible for balancing generation with demand – will instruct NIE Networks to reduce electricity demand through planned emergency power cuts.
    SONI have indicated that Planned Emergency Power Cuts could happen due to a number of factors which may or may not be relevant on any given day.  These include:

    • Unforeseen forced outages of other plant and managing planned maintenance outages
    • Variable demand – winter vs summer demand / peak vs non-peak
    • Variable generation – variability of renewable generation
    • Small-scale nature of NI grid – factors more difficult to balance
    • Introduction of new technologies to help facilitate energy system transition

    Planned emergency power cuts are only implemented to protect the electricity network from more
    damage, which would be more disruptive to customers for a much longer period. They are a
    last resort and wouldn’t affect everyone at the same time.

  • How do we tell the difference between an electric fault and Planned Emergency Power Cuts?

    It is important to determine if your interruption to supply is caused by the Planned Emergency Power Cuts or a network fault. Please check the areas affected by the planned power cuts.  If your area is not included in the Planned Emergency Power Cuts please report this as a fault.

  • How likely to happen are emergency power cuts?

    SONI undertakes a ‘Winter Outlook’ every year which helps to inform the electricity industry and prepare for the winter ahead.  This provides more information on how likely Planned Emergency Power Cuts are.
    As part of this process, SONI takes several steps to protect customers. These include:

    • Asking companies to generate more power to meet the demand and switching on generators which aren’t currently supplying power to the market.
    • Asking heavy industrial users to limit how much power they use during certain hours.
    • Reducing household power usage – this includes asking customers to change how and when they use appliances like washing machines and dishwashers or reducing voltage across the country by a small percentage, which would be undetectable.
  • Would everyone in NI have a power cut at the same time?

    No, planned emergency power cuts do not mean everyone is without power at once. The emergency disconnections are designed to prevent this occurring.

  • Will my neighbours be without power at the same time as me?

    In the vast majority of cases this will be true, but the electricity network is designed in such a way that properties in the same street are often supplied by different electricity cables. In some cases, this means that the electricity cable that supplies your property may be switched off, but the cable that supplies your neighbour’s property is not.

  • Is the network safe? We live close to a substation / transformer / pylon – are we at risk?

    No, the safety of the system is intact but the generation currently doesn’t meet demand.  If Planned Emergency Power Cuts weren’t undertaken the system could become unstable but this relates to the ability to provide power and not the infrastructure itself.

Block Letters & Rota

  • What is a block letter and why is it important?

    Each electricity meter is assigned a ‘block letter’ between A and U. The letters F, I and O are not used.
    The blocks are pre-determined and are designed to represent approximately 5% of the NI Electricity System. The areas affected by each block will be spread geographically across NI and can be found on our Block Map.
    The number of Blocks that need to be disconnected simultaneously will depend on the direction given by SONI as to the level of the generation shortfall.
    The NIE Networks Control Engineers will disconnect the required blocks according to the rota order.
    In the event of a planned emergency power cut, different block letters are timetabled to be without power for typically around three hours once a day. However, depending on the severity of the scenario, power may be interrupted multiple times over the period of the event.

  • How long will I be without electricity supply? Can the times be negotiated?

    Each block will be disconnected for a maximum of three hours at a time. The blocks are also rotated, so that once an area has been taken off supply, that block goes to the bottom of the list so all blocks are used in rotation before that block is used again.  Unfortunately, we cannot negotiate and arrange alternative times at an individual customer level.

  • Where can I find my block letter?

    You can find your block letter by entering your postcode on our Block Map. It is based on where you live and how your electricity is supplied.
    Your block letter is static and will not change during an emergency.

  • How do I know if or when my power will be switched off?

    When a planned emergency power cut starts the rota for power cuts will be published on our website.
    Your power might be switched off or reconnected around 30 minutes before or after the published time depending on electricity use at that time.
    This is because of the need to co-ordinate disconnections and reconnections, creating a short overlap.
    Those who have had their power disconnected will go to the bottom of the timetable and would only be disconnected again if all blocks have had their turn.
    If your power is not restored within an hour of your scheduled time, please visit Power Check for more information and report your power cut.

  • Could I still be affected by planned emergency power cuts, even if my rota block is not affected?

    Even if your rota block is not confirmed for disconnection you should be aware that, in isolated instances, due to the large scale of emergency power cuts, there is a possibility that you may experience some short duration (< 3 min) effects. For example, dimming of lights or low power.
    Please only contact NIE Networks if you continue to experience these issues more than an hour after the emergency power cut has ended.


  • Should businesses do anything to prepare?

    We realise that a reliable electricity supply is crucial for business customers. However, power cuts can happen and often are due to situations out of our control.
    Business owners should think about risks to their business if they experience a power cut.  Consider:

    • Manufacturing processes
    • Refrigerated items
    • Data access
    • Telephone lines
    • Customer orders
    • Accessing your premises
    • Maintaining key business processes.

    Consider plans to manage staff wellbeing as water supply and gas may be affected by a power cut.  Think about staff safety and whether staff can work from an alternative location. 
    It is worth considering if a back-up generator could help or if you already have one checking if it has it been serviced recently.  It is worth having a plan in place and being prepared in the unlikely event of a power cut.

  • Will I get advance notice when there is a planned emergency power cut?

    Planned emergency power cuts may take place without notice if SONI instructs NIE Networks to reduce demand immediately.  Where possible, advance notice will be given through media and social media channels.

  • Can you not give me a generator?

    In an emergency power cut scenario it won’t be possible to connect generators.

  • Should I buy my own generator?

    This is a personal decision and not something we can advise on. If you do choose to connect your own generation, this must be done by a qualified professional.

  • Is there any action I should take in preparation?
    • Refrain from using more electricity in preparation (boiling kettles for flasks, charging mobile phones etc.) as the system is struggling with the demand and a surge from other areas may make the situation more unstable.
    • Remember to open (or shut as appropriate) any electric gates or access points.
    • Check on elderly or vulnerable neighbours, family and friends and make them aware of the Planned Emergency Power Cuts.
    • If working or studying please back up your work before the power is anticipated to go off.
    • Keep a torch handy in case you are without power during the night.
    • Have warm clothes and blankets accessible in case you experience a prolonged power cut.
    • Please note that mobile phone service will be extremely limited and might drop out entirely, if you need to contact people make alternative arrangements.
  • I have a stairlift – what should I do, and how can I prepare?

    Stairlifts often have backup batteries. You should check how long your backup battery is expected to last. If you are unsure, you should speak to your manufacturer.
    Planned Emergency Power Cuts are expected to last around three hours.  You should make sure you have access to a ground floor exit, telephone and heating for the duration of time you are scheduled to be without power.

During A Power Cut

  • Is there any action I should take when power is disconnected?
    • Switch off electric heaters and cookers to avoid a fire risk when the power is restored.
    • Switch off and unplug equipment, including satellite receivers, televisions and computer equipment
    • Leave a light on to tell when the power is restored
    • It may help if you can turn off your central heating time switch while the electricity supply is off as gas and oil central heating boilers generally won’t work without electricity to power their pumps.
    • Check on elderly or vulnerable neighbours, family and friends and make them aware of the Planned Emergency Power Cuts.
    • Listen out for information on local radio, check our website or social media platforms – use a car radio to tune in for hourly news bulletins
    • Keep fridge and freezer doors closed. Contents should be safe for many hours but, if in any doubt, dispose of the food if it appears to have defrosted.
    • To keep warm, stay in one room, or even in bed
    • If you have one, a battery back-up alarm clock may be useful for any overnight or early morning power interruptions
    • It may be necessary to adjust time switches and clocks when your power returns.
  • Will food in my fridge/freezer be ok?

    Food should keep for between 4-6 hours in the fridge and 15-24 hours in the freezer if you can avoid opening it.

  • What about my tropical fish?

    When you have invested a lot of time and money in fish and equipment we want to help you
    look after them during a power cut. Here are some tips:

    • During a power cut the temperature of the water in your tank will drop gradually. This speed depends on the surrounding temperature and the volume of water inside the tank, i.e. a larger volume of water will take longer to cool down than a smaller volume of water.
    • For insulation, wrap the tank in blankets. If possible, fill hot water bottles with warm water and place them around the outside of the tank.
    • Without power, the water will lose oxygen gradually. Fish suppliers recommend a cheap bubble up filter that can run off a battery-powered air pump. If you don’t have one then a normal bicycle pump will do the job.
    • Fish suppliers recommend disturbing the water surface for five minutes each hour during a power cut. A good way is to fill a jug with tank water then pour it back in, making as much movement as possible.
  • Will you provide updates to customers in an event?

    Information will be published on the NIE Networks website ( and social media channels.

  • My power has gone off at a time different to those published, why is this?

    The timing of the rota disconnections can change.
    If the situation deteriorates, NIE Networks may have to begin the rota earlier than originally required.
    If the situation improves, NIE Networks may be able to reduce the number of blocks affected or the duration of the disconnections.

  • What do I do if my electricity does not come back on when I expect it to?

    If your electricity supply has not been restored after four hours, please contact our helpline on 03457643643.

Protected Sites

  • Are any sites protected from the power cuts?

    A very limited number of sites are protected from emergency power cuts. These are typically locations which are deemed to be critical infrastructure, such as air traffic control centres and major hospital facilities with accident and emergency departments.
    It is important to note that residential customers, including those on the NIE Networks Medical Customer Care Register and businesses without backup generation and which are not listed as “protected” by the government, would not be exempt.
    The actions described in ESEC are not used to handle sudden shortfalls in generation, or to deal with day-to-day repair and recovery of faulty or damaged parts of the transmission and distribution networks.  During such events, sites included on the protected sites list may well still experience interruption to their electricity supplies.

  • Can my home or business become a ‘protected site’?

    Homes cannot become ‘protected sites’ as they are not critical national infrastructure.
    Organisations which are not already aware of their protected status will need to apply to NIE Networks to become ‘protected’ as this is not automatic. There are very strict qualifying criteria set out in the Electricity Supply Emergency Code by the Department for Economy.
    To apply, the Application Form should be completed and sent to NIE Networks to review.

  • What about hospitals?

    Most hospitals have backup generators to ensure they can continue to operate in the event
    of power disruption but acute hospitals will also be listed as protected sites.

  • What about hospitals?

    Most hospitals have backup generators to ensure they can continue to operate in the event
    of power disruption but acute hospitals will also be listed as protected sites.

  • What about hospices, care homes, schools and other core services?

    Business continuity plans will vary across specific organisations and service providers. Power cuts can occur at any time so most will have plans in place. It’s sensible to review any additional risks from three hours without electricity, as a precaution.
    Businesses which are responsible for caring for vulnerable customers are always encouraged to ensure they have robust business continuity plans in place, this may include investing in their own emergency back-up generator supply.

  • What about customers with medical needs at home?

    Customers who have signed up for the Medical Customer Care Register should have contingency plans in place with their healthcare provider.  If you are experiencing issues please contact your healthcare provider.

  • What about people that rely on electrical medical equipment?

    In most cases, customers who are medically dependent on electricity will be familiar with the process and limitations of their equipment as power cuts can occur from time-to-time during a typical year, including during severe weather, for regular maintenance or due to damage and other routine faults.
    These customers often have backup power sources to keep vital equipment powered for several hours during a power failure.
    Customers who require a continuous supply of electricity for medical reasons should seek advice from their local health service provider.
    Backup power supplies and associated equipment should be regularly checked and maintained by a competent person. If you're concerned, you should speak to your medical equipment or health care provider now.
    If emergency power cuts are needed customers will be able to find their block and the blocks affected by visiting our website.

  • Why can’t you protect me from these power cuts?

    NIE Networks is legally required to implement power cuts, when instructed by SONI.


How The System Works

  • What is a system operator?

    The Transmission System Operator for Northern Ireland is also known as SONI.
    Their role is to manage the electricity grid, balancing demand and generation to ensure electricity can flow from where it is generated to where it is needed.
    They are also responsible for planning and upgrading the electricity grid.

  • Who are the electricity generators?

    Generation comes from Kilroot, Ballylumford and Coolkeeragh Power Plants which use gas.  
    It also comes increasingly from renewable sources such as wind and solar farms.
    In Northern Ireland we also import electricity through the Moyle Interconnector.

  • What is a Network Operator?

    The network operator for Northern Ireland is Northern Ireland Electricity Networks.
    We are the owner of the electricity transmission and distribution networks in Northern Ireland, transporting electricity from where it is generated to over 910,000 customers including homes, businesses and farms.
    We also connect approximately 9000 customers a year to the electricity network.

  • What is a supplier?

    A supplier is a company that buys wholesale electricity from electricity generators and sells it at a retail level to customers.
    You can choose who supplies your energy. This company is known as your electricity supplier
    and they bill you for the energy you use.
    In Northern Ireland there are 5 suppliers; Power NI, SSE Airtricity, Click Energy, Budget Energy and Electric Ireland.