Nautilus is being developed by National Grid Ventures and is expected to connect up to 1.4 GW of offshore wind energy to the UK and Belgium.

The original plan was for the windmill to come ashore in the UK at Leiston in Suffolk, but due to local dissatisfaction the developer proposed changing this to the Isle of Grain in Kent.

However, Ofgem was planning to reject the proposal due to the cost constraints of the project, i.e. the cost of upgrading the network around Grain to carry the power between Nautilus and the electricity system would be too high.

The plans now revert to the original proposal for the interconnector to come ashore between Sizewell and Thorpeness, near Leiston, with cables running to an interconnector at Friston and connecting to the grid via a yet to be built substation.

While National Grid and Ofgem both support the location changes, Suffolk County Council has said the plans could cause unnecessary harm to the county.

This comes on top of the transmission company’s plans for another HVDC link in Suffolk, the 138km Sea Link to Kent, which is also currently under consultation and has been voiced by campaign groups.

Richard Rout, Suffolk County Council’s deputy cabinet member for nationally significant infrastructure projects, said: “Suffolk is once again bracing itself for the impact of another major energy project. It feels like the same old story, with cost savings being prioritised over the damaging effects on our communities and the environment.

“The Council has always supported the need for the country to ensure energy security.

“But now we are seeing layer upon layer of uncoordinated energy projects impacting Suffolk, irreparably damaging communities, their heritage and their environment. It is ruthless and it is unfair.”

The Council indicated that it will carefully consider the updated plans and their implications, particularly in light of the Sea Link project.

Rout continued: “If Nautilus comes to Suffolk, the Sea Link project, which we also have major concerns about, will need to be reformed to work with it.”

“The new Secretary of State has said he is committed to decarbonising the electricity system by 2030. But that goal must also take serious account of the communities that will live with the new infrastructure.”

“We are also really concerned about the impact on the mental wellbeing of those facing the prospect of new infrastructure. Developers need to recognise their duty of care, because the wellbeing of our communities is at stake.”

The location of the UK connection was originally changed to the Isle of Grain due to community concerns about the number of energy projects taking place in Suffolk. While returning to the originally planned location is expected to reduce costs, Ofgem stated that the new updated plans “may reduce the costs of other applicant projects to varying degrees”.

In addition to the location change, the Belgian authorities have further updated the modelled capacity for connection to a planned offshore wind farm island off the coast of Belgium and the Belgian mainland from 3.5 GW to 1.4 GW. There were previously some uncertainties around this capacity, but Ofgem stated that this has now been clarified.

The analysis further shows that adjustments to Nautilus’ location and capacity indicate a reduction in mitigation costs of more than 50%, reducing the expected cost from the original range of £1.3 billion to £3.3 billion to an updated range of £0.5 billion to £1.4 billion when comparing the low and high estimates.

Ofgem said: “Since the assessment outlined in the minded-to consultation of 1 March 2024, which included a proposal to reject the Nautilus project due to the high cost constraint and the uncertainty in the project’s configuration meaning the impact on UK welfare is uncertain, two key features of the project have changed: its location in the UK and the modelled capacity of the cables connecting the Belgian offshore island to the Belgian coast.”

It was further argued that clarification on the configuration of the Belgian Energy Island would improve the assessment of the project’s maturity and its potential impact on socio-economic well-being.

In view of these changes, Ofgem has decided that the project should be reconsidered in relation to the updated plans.

National Grid said: “Unlike Grain, Friston does have capacity in the electricity system.

“This means the cost of connecting Nautilus at Friston is lower as fewer reinforcements and upgrades are required to transport energy between Nautilus and the wider electricity grid.”

The consultation on Nautilus runs until August 15 and National Grid said it expects “clarity on the future” of the project in the autumn.

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