Electricity Transmission Agreements UK: Key Terms
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If you are developing a renewable generation project in the UK, getting electricity onto the grid is not as simple as flicking a switch. Your project needs a formal arrangement with the relevant network operator that sets out how, where and on what terms your power can flow into the transmission system.
These arrangements are known as transmission agreements, and they sit at the heart of every wind farm, solar park or large battery project that feeds the national grid. The terms you agree on connection capacity, charges and performance obligations will shape the commercial viability of your project for decades.
In this guide I walk through the main concepts you will come across, why each matters, and the practical questions developers tend to wrestle with before signing.
What this document is
A transmission agreement is the contract that governs how a generator, typically a renewable developer, connects to and uses the high voltage transmission network in Great Britain. In broad terms it covers two things: the physical connection to the grid at a specific location, and the ongoing right to import or export electricity across the wider system.
The counterparty is usually the transmission owner for your region (such as National Grid Electricity Transmission in England and Wales, SSEN Transmission in the north of Scotland, or SP Transmission in southern Scotland), working alongside the system operator responsible for balancing the network in real time. Alongside the bilateral connection contract, generators also accede to industry-wide codes such as the Connection and Use of System Code (CUSC) and the Grid Code.
Together these documents fix your connection point, set the capacity you can rely on, establish the charges payable, and impose technical standards you must meet to keep generating.
How to use this document
- Scope out your project and grid options. Before approaching any network operator, get clear on your site, generation technology, expected output and preferred commissioning date. This groundwork lets you ask sensible questions about where you might connect, what capacity could realistically be available in that area, and roughly how long you may be waiting. 2. Apply for a connection offer. You submit an application to the relevant transmission owner or, for many projects, via the system operator. The application triggers studies into network capacity and the works required. You will eventually receive a connection offer setting out the proposed connection point, capacity, charges, construction works and an indicative connection date. 3. Negotiate and accept the offer. Connection offers are not always set in stone. Developers often push back on connection dates, interactive queue positions, security requirements and the scope of reinforcement works being allocated to their project. Once you are comfortable with the terms, you accept the offer and enter into the bilateral connection agreement with the transmission owner. 4. Accede to the industry codes. Operating on the transmission network means signing up to the CUSC and complying with the Grid Code, the Balancing and Settlement Code and other relevant frameworks. These govern use of system charges, balancing, metering and technical performance, and they apply to every generator connected at transmission level regardless of size or technology. 5. Commission, test and start generating. Before you can export commercially you must complete compliance testing to demonstrate your plant meets Grid Code requirements. Once signed off, you move into live operation, start paying ongoing use of system and balancing charges, and remain subject to the availability and performance obligations in your agreement for the life of the project.
Common questions
If you're dealing with this kind of situation, speak to an experienced legal adviser who can walk you through it — from £89.
Common questions
Q Who do I actually sign a transmission agreement with?
For projects connecting at transmission voltages in Great Britain, you contract with the transmission owner whose network covers your site. In England and Wales that is National Grid Electricity Transmission, and in Scotland it is SSEN Transmission or SP Transmission depending on the region. The system operator, currently the National Energy System Operator (NESO), plays a central role in the application and offer process.
Q What is the difference between a connection agreement and use of system terms?
The connection agreement is the bilateral contract covering the physical link between your site and the network, including the connection point, capacity and any reinforcement works. Use of system terms, set out under the CUSC, govern the ongoing right to flow power across the wider transmission network and the charges that come with it. Most generators need both in place.
Q What are transmission use of system (TNUoS) charges?
TNUoS charges are levied on generators and suppliers to recover the cost of installing and maintaining the high voltage transmission network. For generators, charges vary by location, reflecting how much a project adds to or relieves network constraints. They can be a material cost for renewable projects and should be modelled carefully at the development stage.
Q What are balancing charges and why do generators pay them?
Electricity supply and demand must match second by second. The system operator uses the Balancing Mechanism and ancillary services to keep the network stable, and the costs of doing so are recovered from market participants through balancing charges, principally the BSUoS charge. Generators factor these into their revenue models alongside wholesale prices and any support payments.
Q How long does it take to get a transmission connection?
Timescales vary significantly depending on location, the reinforcement works needed, and the overall connection queue. Recent reforms led by NESO and Ofgem are aimed at speeding up offers for viable projects and removing stalled ones. Developers should treat any indicative connection date as a working assumption and check progress regularly throughout construction and planning.
Q Can a transmission agreement be transferred if I sell the project?
In most cases yes, but transfers are not automatic. The bilateral connection agreement and CUSC accession will usually require the network operator's consent and may be subject to credit and security checks on the incoming party. Transfers are a routine part of project finance and M&A in the renewables sector but need to be planned into the transaction timetable.
Q What happens if my project fails to meet its availability or performance standards?
Connection agreements and the Grid Code set out what happens if a generator falls short, which can include loss of capacity rights, requirements to carry out remedial works, or in serious cases disconnection. The precise consequences depend on the terms you have agreed and the nature of the issue, so the technical and commercial clauses deserve close attention during negotiation.
If you're dealing with this kind of situation, speak to an experienced legal adviser who can walk you through it — from £89.
Sources
This guide is based on primary UK law and official guidance.
- Official SourceNational Energy System Operator (NESO): Connectionsneso.energy
- Official SourceConnection and Use of System Code (CUSC)neso.energy
- Official SourceGrid Codeneso.energy
Legal helpline
Questions about connecting your project to the grid?
Transmission agreements are long, technical and commercially significant, and the wrong assumptions on charges or capacity can derail a project. An experienced legal adviser can talk through the key terms with you on the phone and help you think through what to focus on, based on what you describe about your project.
- A plain-English walk through the key terms of transmission agreements
- Practical perspective on charges, capacity and connection timing for your situation
- Points to watch out for when reviewing an offer from a network operator
- Clarity on your next steps before committing to any contract
Legal disclaimer
This article is for general information only. It is a tool to help you find your way — not legal advice, and not a substitute for speaking to a qualified adviser about your situation.