Key messages

The ETYS is the ESO’s view of future transmission requirements and the capability of Great Britain’s National Electricity Transmission System (NETS).

The ETYS sits at the heart of our network planning process.

Find out more about our vision for Great Britain’s energy network.

We use the analysis in our Future Energy Scenarios (FES) to tell us what generation and demand could look like over the next 30 years.

Using this data, we identify the points on the transmission network where new requirements are needed to help us continue to deliver electricity reliably.

Our ambition

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

By 2025, we aim to have:

An electricity system that can operate carbon free

A whole system strategy that supports net zero by 2050

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.

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 the points on the transmission network where more network transfer capacity is needed to help us continue to deliver electricity reliably.

Once we know what the network requirements are, we invite stakeholders to propose solutions that will be needed to meet these requirements. These proposals are then assessed through our Network Options Assessment (NOA) process, where the most economic and efficient solution is given a recommendation to proceed, and others told to hold or stop

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Key Messages

Click on the boxes below to expand on the key messages for this year.

Key message 1: Power flows will become more variable with higher peaks

Over the next 10 years, wind generation is forecast to increase to 40GW across the country.

The demand is predominantly located in the south of the country leading to high north-south power flows with high variability.

Interconnectors connect us to other European markets and either import or export power. As these flows change, it can require further transmission capability on the system especially when interconnectors export to Europe during significant wind output

Key message 2: In the move to net zero over the next decade, the GB Electricity Transmission System will face growing needs in a number of regions

1	Increasing quantities of wind generation connected across the Scottish networks more than doubling the north-to-south transfer.	Additional 4GW of renewables expected compared to last year’s scenarios resulting in a total of 18GW of required transfer by 2040.
2	A potential growth of over 6GW in low-carbon generation and interconnectors in the North of England combined with high Scottish generation, will increase transfer requirements in the Midlands.	25% increase in expected requirements compared to last year’s scenarios.
3	10GW increase expected in generation coming from offshore wind on the east coast connecting to East Anglia, which will increase the need for reinforcement here.	17% increase in expected generation between Two Degrees (FES 2019) and Leading the Way (FES 2020).
4	New interconnectors with Europe will place increased requirements on the transmission network.	17% increase in expected generation between Two Degrees (FES 2019) and Leading the Way (FES 2020).

Key message 3: Constraint costs are expected to increase due to high flows across the transmission boundaries if no action is taken over the next ten years

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

The numbers above correspond to the points from the map in Key Message 2

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

The heatmap shows that if no reinforcements are made to the system (i.e. the system is the same as it is today, over the next 10 years), the network boundaries defined in the ETYS would lead to incurring significant network constraint costs due to the high flows from the increased generation capacity.

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Improving our analysis

Our new analysis techniques enable us to look at more detailed year-round thermal requirements.

The power transfer capability across the network throughout the year is constantly changing and we are always trying to maximize the capability of the transmission network. As the ESO, we securely and economically operate the transmission network.

The graph shows the number of scenarios throughout the year for a particular power transfer level across the boundary, how many scenarios had no overloads, so acceptable (blue), and how many scenarios had at least 1 asset overloading which is unacceptable (orange).

Defining the network capability is complex. The overlap in the graph shows that a particular level of power transfer across a boundary could be either “acceptable” or “unacceptable” which is dependent on the generation and demand scenario. Our new analysis techniques allow us to model this complexity and calculate the likelihood and impact of differing network conditions throughout the course of a year.

We can also assess solutions by applying year-round conditions to help identify an optimal solution which extends our traditional analysis and opens the opportunity for a wider range of network and non-network solutions.

We will be learning from these techniques and investigating how to integrate the analysis within the NOA and how it could evolve to capture both thermal and voltage issues.

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