Preparations for Winter ‘22: The UK’s Electricity Supply Emergency Code Explained

We have established this page to provide useful information, resources and updates related to the Government’s Electricity Supply Emergency Code (ESEC), which outlines the Rota Load Disconnection process that would be activated in the event of UK power supply shortages.

National Grid’s 2022 Winter Outlook Report outlines the range of scenarios that could occur this winter, which includes the potential for supply shortages. With the possibility of blackout periods, it’s important to be aware of the Electricity Supply Emergency Code (ESEC), which details precautionary measures to be enacted in the ‘unlikely’ event that the UK experiences insufficient gas for power generation.  

The government’s ESEC includes a ‘Rota Load Disconnection’ measure, which involves power being disconnected from specific areas for defined periods of time, on a rotating basis across the country.

We have compiled a number of FAQs and important industry contacts to help you plan ahead.

Emergency contact information and resources:

> Distribution Network Operators (DNOs) contact information

> National Grid ESO Winter Outlook Report


> Energy Networks Association

> Priority Services Registration

Call 105 for general information on power cuts


  • What is my Alpha Identifier?

    An Alpha Identifier is the letter allocated to business energy customers in a particular block. If required, the National Grid will refer to these letters when announcing supply emergency measures to inform businesses if their ‘block’ will be impacted.
    SmartestEnergy Limited customers will find their Rota Load Disconnection Alpha Identifier on their bill under the site information section (on the right-hand-side) beneath their MPAN number. See screenshot below FAQs.

    SmartestEnergy Business Limited customers will be notified of their Rota Block Disconnection Alpha Identifier by letter which will be sent by email directly to the billing contact held on account record. You can also check your Alpha Identifier and local Distribution Network Operator (DNO) via the find operator tool at

  • What if I don’t have an Alpha Identifier on my bill?

    If there is no code provided on your bill, your postcode might not have been allocated an Alpha Identifier by your Network Operator or we might have an incorrect postcode. We are looking to communicate to all customers who do not have an identifier to confirm their postcode and complete the necessary checks with industry bodies. If you don’t have an Alpha Identifier, please contact +44 1473 234151 or [email protected]

  • What should businesses do to plan ahead this winter?

    In a planned power cut scenario, National Grid aim to provide advanced notice so businesses can plan ahead.

    The country is split into 18 ‘Blocks’ which are each made up of a number of discrete geographical areas.

    Each of these blocks are assigned an alphabetic letter (known as an 'Alpha Identifier'). The alphabetic letter assigned is linked to the postcode.

    The blocks are allocated to the slots in such a way as to allow businesses in any given block to operate as normally as possible for 3 days in succession. This means that power cuts will either be concentrated between Monday and Wednesday, or Thursday and Saturday with Sunday being shared between all blocks.

    Customers should speak to their insurance companies to understand if any losses would be covered.

    See the above FAQ for how to locate your Alpha Identifier.

  • Will I still be charged for energy that I don’t consume?

    You will only be charged for the amount of electricity based on your meter readings. If you do not consume due to a planned power cut scenario, you will not be charged for electricity during the outage. If you are a NHH customer, please submit meter readings to ensure that we can verify your usage by contacting [email protected]

  • What is a protected customer?

    The Electricity Supply Emergency Code (ESEC) defines a protected customer as any person whose name appears on one of the lists of protected customers which is to be compiled and kept up to date by Distribution Network Operators (DNOs). In the event of Rota Load Disconnection, the local DNO must ensure supply to registered protected customers for as long as practical. Protected customers include hospitals, hospices, schools, health facilities, food manufacturers, essential transport, etc.

  • What is the criteria to go on the protected customer list?

    The criteria to be considered for the protected customer list consists of two elements that must be met:

    1) Your site must fall within the list of approved designated services published in the Electricity Supply Emergency Code (ESEC).

    2) Protected sites must also meet additional criteria, whereby the customer has demonstrated that it is not possible to install standby generation. For more information about the criteria, please view the Electricity Supply Emergency Code (ESEC) published November 2019 on

  • How do I apply to go on the protected industry list?

    Customers will need to contact their local Distribution Network Operator (DNO) if they believe they fall under any of the classifications of a protected customer.

  • What if I classify as vulnerable customer?

    A vulnerable customer could be someone classified as elderly or medically dependent on electricity (e.g., dialysis machines). If you believe you fall under this category in your business activities, you should register for the ‘Priority Services Register’. More information can be found here

  • How likely is it that the ESEC will be invoked this winter?

    In the National Grid ESO Winter Outlook (published 6th October 2022), a number of scenarios are listed. Scenario 2 covers the unlikely event that the UK is impacted by insufficient gas for power generation with reduced electricity imports from Europe. Under this scenario, National Grid cautions that the ESEC will need to be invoked.

  • In the event of Rota Load Disconnection, how long could my business be without power for?

    The electricity supply will be turned off block-by-block for a three-hour slot at a time, depending on the shortfall of electricity. The shortfall can change throughout the day and is dependent on the weather, the time of day, the time of year and the demand for electricity. At the lowest level of emergency, you could expect to be without electricity for three slots in a week.

  • How will this impact my generation asset?

    In the event of Rota Load Disconnection, businesses with on-site generation assets will be disconnected along with site-related imports. For larger embedded generators, it is likely that the DNO would isolate the circuits that have generation on them within the load control area to allow them to keep exporting. However, this would not be guaranteed. Please contact your DNO to confirm whether there is any risk of curtailment during a rota block disconnection.

  • Where can I find more energy advice?

    Stay #EnergyAware this winter with useful advice from Ofgem's new Energy Aware Business hub. Ofgem will be sharing lots of handy guides and quick tips on controlling your energy usage, energy efficiency schemes and more to help you manage your energy this winter.


SmartestEnergy Limited customers – locate your Alpha Identifier on bills:

As an I&C Supply customer, you will find your Rota Load Disconnection Alpha Identifier on your bill under the site information section (on the right-hand-side) beneath their MPAN number. See screenshot below: