The Electricity Ten Year Statement (ETYS) is the ESO’s view of future transmission requirements and the capability of Great Britain’s National Electricity Transmission System (NETS) over the next 10 years.

The ETYS is important in helping us to understand what investment and development is needed to help us achieve our zero-carbon ambition. ETYS 2021’s key messages explain some of the most pressing issues we see on the NETS as we drive towards net-zero.

As we emerge from the initial impacts of COVID-19, the past year has reminded us all how much our decisions matter in response to global issues – and we’ve also seen how far we can adapt to major changes.

About the ETYS

The ETYS sits at the heart of our network planning process. Using the data from our Future Energy Scenarios (FES), we identify points on the transmission network where more transfer capacity is needed to continue to deliver electricity reliably.

Once we have assessed the network requirements, we invite stakeholders to propose solutions to these requirements. These proposals are assessed through our Network Options Assessment (NOA) process, where the most economic and efficient solution is given a recommendation to proceed, and others put on hold or stop.

ETYS and the network planning process

What's new

Last year, we published a web version of the ETYS for the first time. This was well received, and we have continued to make improvements so that our web version of ETYS 2021 is clearer and easier to use for our readers.

We have removed the section on ‘Year-round probabilistic analysis’ included last year as we will present our probabilistic tool developments in a separate publication, due in Q1 2022.

In response to the feedback received by the ESO, this year, the ETYS boundary charts have an indicative boundary transfer capability based on the 2020/21 NOA optimal path. We hope this allows the reader to see the capability of the system and opportunities over the future years as well.

Key messages

1. Growth in north-south power flows continues with high variability

The past year has seen increased ambition for offshore wind, with the Government’s Ten Point Plan re-affirming the commitment to reach 40 GW of installed capacity by 2030.

Electricity demand is predominantly located in the south, leading to high north-south power flows. These flows are highly variable due to the intermittent nature of wind generation and interconnection. The system will need to be prepared to manage large swings in power flows.

The north-south flows contribute significantly to system constraints across the entire GB transmission system.

 

2. In the next decade the GB Electricity Transmission System will face growing needs in a number of regions

1

A tripling of wind generation connected across the Scottish networks by 2030, driving higher north-to-south power transfers.

2

A doubling at least of transfer requirements from northern Scotland to the Midlands over the next 10 years. Major new reinforcements will be required to facilitate these power flows through the North of England.

3

Up to a 12GW increase in transmission-connected low-carbon and renewable generation is expected in East Anglia between 2020 & 2030, a 2GW increase on the forecast from ETYS 2020. New interconnectors connecting in the region will add to transfer requirements even during low-wind periods.

4

New interconnectors with Europe will place increased requirements on the transmission network, interconnector capacity is anticipated to exceed transmission connected generation in the South of England.

 

3. Timely delivery of network reinforcements in the NOA will significantly help reduce network constraints

The ETYS describes the network capability by looking at the maximum secured power transfer between two regions or the power transfer across a boundary.

To operate the network safely, we must make sure that the power flow across the boundary do not exceed the capability of the system between the two regions. To prevent this, we must take actions to constrain generation which can incur significant costs.

The heatmap (top-right) shows that if no reinforcements are made (i.e., if over the next 10 years the network remains the same as it is today), the boundaries defined in the ETYS would be significantly constrained due to high flows from the increased generation capacity.

Due to the growth in government ambition reflected in FES 2021, our boundary flow requirements are higher than last year. To reduce network constraints, the NOA 2020/21 recommended a number of options and their effect can be seen on the heatmap on the bottom right. NOA 2021/22 will be looking to recommend options to address these growing system needs. Also, the ESO is progressing the five-point plan to further tackle network constraints.

Excess flows beyond boundary capability if no action is taken to reinforce the system.

Excess flows beyond boundary capability with NOA 2020/21 recommended options applied*.

*Chart uses the 2020/21 NOA recommendations against Leading the Way scenario in 2021/22 FES flows.

About the ESO

Electricity is a modern-day necessity and the ESO exists to make sure everyone gets access to a safe, reliable and affordable supply. We make sure people, communities and businesses across Great Britain have the electricity they need at the flick of a switch because without it, society and the economy wouldn’t function. We bring energy to life.

But providing reliable and affordable electricity is not enough. The energy we all consume needs to get cleaner, quickly. We are passionate about making a difference and delivering that change. We are here to help Great Britain and other countries reduce their carbon emissions so that our planet is safe for future generations to enjoy.

Our mission is to enable the transformation to a sustainable energy system and ensure the delivery of reliable, affordable energy for all consumers.

By 2025, we're aiming for:

This means we need to fundamentally change how our system is designed to operate. We are working with the industry to integrate newer technologies across the system and increase demand-side participation.

ETYS 2021

View our PDF version of the full ETYS publication.

Download the full ETYS publication

Discover more about ETYS

ETYS and the Network Planning Process

Learn about how we prepare the ETYS and how it fits with our network planning process.

Electricity transmission network requirements

You can discover more about the various regions of the transmission system and their capabilities.

Way forward

Read how we are going to improve the ETYS and how you can get involved.

ETYS documents

Get to the appendices, glossary and other helpful contact information.