Ahead of consultation, we conducted a full backcheck of the options for reinforcement of the East Anglia electricity network to meet the future needs of net zero and increasing demand for electricity. This was published in June 2023 and can be found on the project website. We considered the issues associated with the subsea option.
Due to the infrastructure required for a sea-based connection, the cost of building an offshore, under sea connection would be around £4 billion. When you compare that to the estimated £895m cost to build an onshore connection, this is an important consideration.
As a regulated business, we need to consider a range of factors to put forward the right solution and ensure good value for UK bill payers. We believe the current proposal provides this solution and is appropriate and consistent with Government policy.
A question on comparable cost has also been raised on National Grid’s Sea Link project, which as a sea-based connection, presents costs as being relatively similar to an onshore connection. There are many technical reasons why the two projects are not comparable, including capacity. The Norwich to Tilbury connection will connect around three times more electricity than that of Sea Link, which would have a significant impact on the cost to build and operate.
It is technically possible to connect the offshore wind generation to Tilbury. However, subsea links have a maximum capacity of 2000 MW, so to match the 6000 MW that the overhead lines can carry, we would need to propose three new offshore cable links.
An offshore connection would also need new infrastructure on land, including cables from Norwich out to the coast, as well as convertor stations at each end of the cables.
When we assess options, there are times when we feel a subsea connection is the most appropriate proposal, but this is not the case for Norwich to Tilbury. We are also planning to build a sea connection, Sea Link, to carry power out of East Anglia. Sea Link would carry 2,000 MW between Kent and Suffolk and, in this instance, a subsea option was assessed as the most cost-efficient option.