This is a high level view of the connections process from start to finish. There are also some useful resources to help you along the way, from applying for your connection agreement, to disconnecting from the National Electricity Transmission System (NETS).

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Managing your Connection

You’ll need a pre-application meeting whether you’re a new or existing customer. It can cover a range of topics, but its purpose is to provide you with all the information you need to submit an application to us at National Grid ESO. There’s more information about the pre-application process on the Connections offer process page.

For a detailed guide to applying for a connection agreement go to the Connections offer process page. When you apply for a connection, you’ll need a good idea of what your connection project will look like as you’ll need to provide the following information:

  • Project size / capacity (MW)
  • Project type (e.g. demand, generation)
  • Fuel type ( e.g. wind, solar, CCGT, battery)
  • Connection point location
  • Outline of project timescales
  • Consenting requirements
  • Ability to provide relevant technical information

Together with the relevant TO, we’ll assist you throughout the pre-application process to make sure you have all the information you need to apply for a connection. Once you’ve been through the connection offer process and your agreement has been signed, you’ll become a contracted party. At this point you’ll need to place securities for your project.

After signing, you might need to modify your contract. For example, if there’s been a change to the project timings, capacity requirements, or technology. Speak to your ESO Connections Contract Manager to find out if you’ll need to submit a Modification application.

To submit a Modification application, you’ll need to:

  • Complete a modification application form
  • Provide the technical data required by the Data Registration Code (DRC) using the DRC tool
  • Pay the application fee

This process applies to changes being made to contracts at the pre-commissioning and post-commissioning stage.

It’s worth noting that if you want to postpone your connection date then charges may apply. For projects in England and Wales the charge is calculated on a pro rata basis and is payable in monthly instalments from the original date of connection to 31 March in the financial year prior to the one in which the Transmission Entry Capacity (TEC) applies. You can calculate the charge using the investment ahead of TEC calculator.

Once you’re a contracted party with National Grid ESO, we are both obliged to meet certain milestones, as set out in the Construction Agreement. If market conditions or anything else are affecting your ability to meet your construction programme then speak to your ESO Connections Contract Manager.

Missed milestones often lead to Modification applications, which mean your project will be re-studied for a later connection date and your programme will be adjusted.

In some cases, where milestones are missed and a Modification application isn’t made, we may have to invoke the clauses in the Construction Agreement that can lead to termination.

After the consenting and financial investment decision, or sanction of your project, you and the relevant TO will begin construction of the works set out in your Construction Agreement. Your ESO Connections Contract Manager will be on hand to answer any questions or facilitate conversations with the TO about the construction of your project.

If you have an agreement with us then you’ll need to satisfy certain Grid Code compliance obligations before becoming operational. The compliance process usually starts about 12 months before commissioning and towards the end of construction.

Once you’ve completed all the steps in the compliance process, we will be able to issue your Operational Notification Certificate. There are a few different Operational Notifications, which are used in different situations:

  • Energisation Operational Notification (EON) – needed for the first energisation of a new connection.
  • Interim Operational Notification (ION) – needed for the first export to the NETS for a new generator connection. For offshore connections, the ION is divided into two parts dealing with offshore transmission system assets and generator assets respectively.
  • ION Part A – needed to connect dynamically controlled assets for the purposes of active control of voltage and reactive power, but not for the purpose of exporting active power
  • ION Part B – needed to connect generator assets for the purposes of exporting active power.
  • Final Operational Notification – issued when all compliance issues have been resolved
  • Limited Operational Notification (LON) – issued to a site that once held a FON but still has a compliance issue to resolve (either from a modification or a fault).

When your construction programme has been completed and your Operational Notification has been issued, your connection can go live. This point you’ll become a connected party and you can import or export on or off the NETS as appropriate under the terms of your contract.

Once you’re connected and all the works are complete, your Construction Agreement will fall away, but your connection or generation contract will stay in place for the life of your project.

When you become commercially available you will start to pay Transmission Use of System charges, plus any charges for connection assets set out in your contract, as well as post-commissioning securities.

You will need to formally notify us if you intend to disconnect from the system and terminate your contracts. Contact your ESO Connections Contract Manager for more information about the disconnection process.

Essential application resources

Download resources to help you through your connections journey.

From March 28 2024, all new onshore transmission applications are required to submit a Letter of Authority as part of the connections application process (CUSC modification CMP427). This provides the ESO with confirmation that the project developer has either formally engaged in discussions with the landowner(s) in respect to the land rights needed to enable the construction of the project on the land, or to demonstrate land ownership.

This change means that new onshore transmission connection applications require a Letter of Authority alongside existing application criteria in order to be considered valid and complete. Failure to provide a valid Letter of Authority will result in an application being rejected.

Ofgem decision on Letter of Authority

Letter of Authority templates

Template A - to be used by landowner where Connecting Customer is not the landowner of the site or is yet to obtain relevant rights to the site

Download Template A

Template B - to be used by the connecting customer where connecting customer is the landowner of the site OR has already obtained the required rights to

Download Template B

Download our guidance document Download the Letter of Authority Q&A

Watch the March 2024 Letter of Authority teach-in webinar

This file contains all the connection application forms for different types of agreements including the modification form.

Application Forms

The Data Registration Code (DRC) sets out the data that’s needed at each stage of the connections process. You can provide this data using the DRC tool, which can be populated with Excel.

DRC tool

Your application fees will depend on your connection type, and the size and location of your project. You can work out how much you’ll need to pay using our application fee calculator.

Application fee calculator


Help and support

We’ve brought together some tools and resources that we think will help you along your connections journey such as a glossary, FAQ's page and how to contact us.