The connections process is key to delivering the capacity needed for an efficient and renewable transmission network.

But how does the process work, and what should you expect across your project journey? Read about our customer connection stages below.

1. Researching your connection

There are several key points to consider before you submit an application to connect to the high voltage electricity transmission system in England and Wales. These include, but are not limited to:

  • Connection type 
  • Connection size 
  • Connection date 
  • Location
  • Planning consents

Our Research Assistant tool was designed to assist with this stage of the process. It will demonstrate the different connection timescales and potential locations for a specific size and type of connection.

Its also important to be aware of all the relevant grid codes all transmission system connected parties must follow. Visit these links below to understand more:

Once you are ready to express interest, submit a pre application request via the Electricity System Operator portal here. This will register you as interested in a particular area, and you can receive an invite to a regional webinar, hosted by NGET and the ESO. Please visit the page previously linked for more details on how to register. The portal will be used throughout your whole connections journey through connections through to decommissioning.

2. Applying to connect and receiving your offer

Once you’ve researched your connection, and are ready to submit your application, visit the Electricity System Operator portal. This replaces the previous connection application form process.

Once the ESO have reviewed the application, it will be sent over to us. A specialised team including your dedicated Account Manager, Power System Engineers and Feasibility Engineers, will work with you to design your connection to the network. To do this, they will use industry standards, such as the Security and Quality of Supply Standard (SQSS), to ensure your connection offer is the most economic and efficient solution. Our Power Systems Engineers also undertake computer-based study work to assess the electrical impact of your connection on the network. Your application will follow the below series of studies.


Thermal studies: Determines power flow requirementsThese studies calculate the current flowing through the power system, to ensure our assets have enough capacity to support your connection. All our assets have thermal ratings, so the study will show if an increased power flow due to the new connection remains within the safe rating of that asset. 
Voltage studies: Determines requirements for any additional reactive compensation devicesVoltage studies may be undertaken to examine any potential voltage instability, voltage control coordination, or to calculate voltage step changes. This will allow us to understand if any new voltage compensation measures alongside your connection may be needed in case of any instability on the network.
Fault level studies: Determines required rating of circuit breakersThese studies determine the size of the circuit breakers needed in line with your connection, to preserve the safety of the equipment should a fault occur. To calculate fault currents correctly, we replicate worst case scenarios to ensure the system can handle all fault conditions.
Stability studies: Determines any transient stability issuesThis assessment looks at the ability of generators to remain stable under normal operating conditions and following a disturbance on the transmission system.


Once your connection design has been agreed, your Account Manager will collate all the relevant information into a contract which is then sent to the ESO and a connection agreement contract will be sent to you.

The period between the ESO sending the connections contract over to us, and us sending it back to ESO during which these processes happen is called a ‘clock start’. See the table below for more information on all the stages of the clock start process.



Key developments that take place after 'clock start'


Setting up your team

We'll put together your NGET core scheme team, which will support you throughout the connection process. This team will be made up of:

  • A power system engineer- conducts the system studies needed for your connection
  • Connection engineer- puts together a project program by bringing costs together, whilst verifying how to deliver the works.
  • Customer Account Manager- your first point of contact for all enquiries relating to NGET. They help manage your needs and requirements.
  • Revenue Analyst- Analyses the costs that will be incurred for your connection, to calculate charging elements appropriate and details them in the offer.
  • Customer Contract Manager- your ESO account manager will remain your primary ESO contact and will be present throughout the connections process.

The team will kick things off internally by running through your application so that we fully understand all of your connection requirements. If any questions arise these will be raised with you.

Analysing your connection requirements

Next, the system studies are carried out. These studies are conducted based on the data the user provides to us. It may comprise thermal studies, fault level studies, voltage studies and stability studies as outlined in the previous table. The depth of these studies is defined by the data the user provides.

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Designing your connection

We will then set up an internal offer workshop. This takes into account the study results and determines the best design for your connection. The connection engineer will then develop your solution further, conducting desktop exercises to calculate relevant costs, designs, and programme. We'll contact you to update you with progress made plus initial views of what your offer may look like.


Drawing up your offer

Once this workshop is complete, we will call you to discuss our proposed offer. We will then hold an internal governance meetings, where we will seek approval to release our offer to the ESO, on your behalf. Following this, we will produce your Transmission Owner Connection Offer (TOCO), which is then sent to the ESO.

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Final amendments

In the final 30 days of the process, the ESO will feedback on any amendments of the Transmission Owner Connection Offer (TOCO) NGET will aim to resolve these as soon as possible. Once this is complete, the user will receive their offer from the ESO.




3. Designing your connection

Once you have signed your connection offer, we will, in the appropriate timescales according to your connection date, progress your offer to detailed design.

The detailed design will consider engineering and environmental assessments, as well as discussions around equipment needed.

Regular progress checks will be undertaken to ensure both yourself and NGET are reaching key construction milestones for your project.

Permitted development rights

Customers are responsible for securing the appropriate planning consents for customer works, including works which may take place on land owned by NGET. Customers may not rely on NGET’s permitted development rights (which are reserved for the benefit of NGET’s transmission undertaking/NGET operational land) to undertake customer works, and should therefore ensure that they can demonstrate that appropriate consents are in place for all customer works, including on NGET land. 

Please note: if you are undertaking a User Self Build then you will take responsibility for this step of the connection works. Find out more here.

If at any point during this stage you need to change any project requirements, you must submit a modification application to the ESO. This is a formal Connection and Use of System Code to make changes to your existing agreement. This will incur a fee and will follow the same offer process as your original application. A modification application will be submitted via the ESO connections portal.

The activities in this stage will be led by our Investment Engineers who may contact you to discuss your connection further and understand site access routes or connection design. The Investment Engineer will also be supported by our Consents team if there are any consenting activities being undertaken by NGET on your project. Your Account Manager will also remain a key contact to check on progress against milestones and manage any updates.

4. Building the connection

During the building process, further surveys and assessments will be done, as well as organisation of contractors and equipment. We will also agree on site responsibilities with you. After this, our construction team will start building your connection in line with your construction programme.

During this stage the construction Project Manager takes over and manages the complete build of the connection - from tender of major items, to managing principal contractors. They will be your main contact in relation to progress at site, coordination of construction activities and commissioning. Connection milestones will also be monitored through regular progress updates with your Account Manager alongside your Project Manager.

5. Connecting to and operating the system

Once the connection assets have been built to specification, and your project is ready to go, you will enter an operational notification compliance process. This will ensure your asset is safe to begin operating.  A Compliance Manager from National Grid ESO will be assigned to guide you through what you need to provide during the process, for example, compliance statements.

Completion of this process provides you with a certificate which allows you to commission your asset. A commissioning panel will then be set up to discuss the stages of your commissioning and allocate responsibilities, such as planning outages and registering any settlement metering in accordance with the balancing and settlement code. Following commissioning, your asset will be operational.

For further information, please refer to the ESO page on the full compliance process.

If you are conducting a User Self Build project, the process will differ. Guidance is available here.

6. Maintaining your connection

When your asset has become operational, you will need to comply with operational Grid Code requirements.

These include coordinated outage planning for work on our transmission assets; and providing regular technical data updates. The Transmission Network Control Centre (TNCC) will contact you in relation to outages required on the system. 

Throughout the life of your connection, you will pay ongoing use of system costs to the ESO, which covers the costs of maintaining the transmission network and day-to-day costs of balancing the energy system. You may also continue to pay for your connection assets, depending on the payment option you select.

For more information on the Grid code, click here.

During the life of your connection, you might plan to modify or re-plant your connection equipment. The size and nature of this may mean it requires a modification application, which you can submit to the Electricity System Operator (ESO) through the connections portal.

During this stage, our Unlicensed business, Engineering and Consultancy Solutions (ECS) can help to assist you. Through this part of our business, we provide various additional services, including asset maintenance and refurbishment of customers' equipment, technical support, and consultancy.

7. Concluding your connection

When you are ready to end your contract with us, you must give written notice to the Electricity System Operator (ESO) declaring your intention to terminate.

Please ensure you discuss ending your contract with your account manager in both NGET and the ESO. Once written notice is then submitted, the process can begin. Our teams will then work with you to identify if any assets need to be disconnected, and whether you need to reduce your outputs or intakes in advance of your disconnection.

Once this work is finished, you will receive formal confirmation that your contract is terminated, a certificate of disconnection removing you from the balancing mechanism, and a reconciliation of outstanding costs.