East of England boundaries

The East of England region includes the counties of Norfolk and Suffolk. This includes the EC5 boundary.

The figure below shows the general pattern of power flow directions expected to occur most of the time in the years to come up to 2031, i.e. power will generally flow from north to south. The arrows in the diagram illustrate power flow directions and are approximately scaled relative to the winter peak flows.

Regional drivers

The arrows in the diagram are meant to illustrate power flow directions and an approximate scale to the flow magnitude in winter peak.

East bounday map 2021

The future energy scenarios highlight that generation between 8 and 18GW could be expected to connect within this region by 2030. Peak gross demand in the East of England region is expected to be remain steady or potentially rise by up to 1GW.

All scenarios show that, in the years to come, large amounts of low-carbon generation, predominantly wind, can be expected to connect. Fossil fuel generation is expected to remain steady within this region and interconnector capacity is expected to rise. The total generation in all the scenarios will exceed the local demand; thus the East of England will be a power exporting region.

East Generator 2021

Currently, there is around 8GW of transmission-connected generation in the region, by 2030 this is expected to increase to between 16 – 25 GW, due to the increasing amounts of offshore wind and interconnectors connecting in this region in the near future. Renewable generation capacity in the region rises from 4.5GW to between 10 – 17 GW across the four scenarios. Large offshore wind projects will be landing and connecting in this region within the next ten years.

The East Anglia transmission network to which the future generation will connect has eight 400kV double circuits. The potential future increase in generation within this region could force the network to experience very heavy circuit loading, stability issues and voltage depressions – for power transfer scenarios from East Anglia to London and south east England. This is explained as follows:


  • The East of England region is connected by several sets of long 400kV double circuits, including Bramford Pelham/Braintree, Walpole–Spalding North/Bicker Fenn and Walpole–Burwell Main. 

    During a fault on any one set of these circuits, power exported from this region is forced to reroute. This causes some of the power to flow through a much longer distance to reach the rest of the system, predominantly the Greater London and South East England networks via the East Anglia region. 

  • Stability becomes an additional concern when some of the large generators connect, further increasing the size of the generation group in the area connected to the network.

    Losing a set of double circuits to a fault will lead to significant exposure to a risk of instability as power transfer increases.

The graph below shows snapshots of the peak gross demand and local embedded generation for the East of England across the four different scenarios. 

East Demand 2021

In a highly decentralised scenario like Leading the Way, local generation capacity connected at the distribution level in this eastern region could reach over 7GW by 2040. Of that capacity, a typical embedded generation output on average might be around 2GW. This will vary depending on factors like wind speeds, and how other local generators decide to participate in the market.

The need for network reinforcement to address the abovementioned potential capability issues will be evaluated in the NOA 2021/22 CBA.

Boundary regions

Click on the regions below to expand the boundary and understand its capability and challenges.

Interpreting boundary graphs

The graphs show a distribution of power flows for each of our Future Energy Scenarios, in addition to the boundary power transfer capability and NETS SQSS requirements for the next twenty years. ​

Each scenario has different generation and demand so produces different boundary power flow expectations. From applying the methodology in the NETS SQSS for wider boundary planning requirements (as discussed in chapter 2), we determine for each scenario:

  • The economy criteria - solid coloured line

  • Security criteria - dashed coloured line

  • Current boundary capability – solid black line

Due to the NOA being published after the ETYS, the boundary capability line (red line) is prepared from the 2020/21 (previous year’s) NOA optimal path released in January 2021 which uses the 2020/21 FES and ETYS data. This is the best information available at the time of publication and will change annually and over time as the network, generation, demand and more importantly the NOA optimal path changes. More information about the NOA methodology can be found here. The 50%, 90%, Economy RT and Security RT are calculated from the 2021/22 FES and ETYS processes. Where the NOA transfer capability is not available, there is a black line that provides the current ETYS 2021/22 transfer capability​.

Note: Boundary capability line is affected by the generation and demand profiles within each FES background. Therefore, the graphs are provided for indicative purposes only and cannot be directly compared. ​

The calculations of the annual boundary flow are based on unconstrained market operation, meaning network restrictions are not applied. This way, the minimum cost generation output profile can be found. We can see where the expected future growing needs could be by looking at the power flows in comparison with boundary capability.​

On each graph, the two shaded areas provide confidence as to what the power flows would be across each boundary:

  • The darker region shows 50% of the annual power flows

  • The lighter region shows 90% of the annual power flows​

From the regions, we can show how often the power flows expected in the region split by the boundary are within its capability (red line). If the capability of the boundary is lower than the two regions over the next 20 years, there might be a need for reinforcements to increase the capability. However, if the line is above the shaded regions, it shows that there should be sufficient capability here and that potentially no reinforcements are needed from a free market power flow perspective until the shaded regions exceed the capability (red line).

Boundary EC5 – East Anglia


Boundary flows and base capability

The capability line (in red) is based on the recommendations from the NOA 2020/21 optimal path which uses the 2020/21 FES and ETYS data as inputs. The 50%, 90% Economy RT and Security RT lines are based on FES 2021/22.

The current boundary capability is limited to 3.5GW due to a voltage compliance constraintat the Burwell Main substation.

The coastline and waters around East Anglia are attractive for the connection of offshore wind projects, including the large East Anglia Round 3 offshore zone that lies directly to the east.​

The existing nuclear generation site at Sizewell is one of the approved sites selected for new nuclear generation development. A new interconnector project is also contracted to connect within this boundary.​

The growth in offshore wind, nuclear generation and interconnector capacities connecting behind this boundary greatly increase the power transfer requirements. The present boundary capability is sufficient for today’s needs but could be significantly short of the future capability requirements.​

In all scenarios, the SQSS economy required transfer and expected power flows grow rapidly from around 2023 to beyond the present boundary capability. This suggests a need for network development to manage the increasing power flows.