National Grid is planning an underwater tunnel across Morecambe Bay as part of an overhaul of its network in west Cumbria.
The energy infrastructure company needs to install new power cables to connect the grid to the proposed 3.4GW nuclear power station at Moorside, near Sellafield, and offshore windfarms in the Irish Sea.
National Grid said its preferred option is to install new cables from west Cumbria to Carlisle, and new cables from west Cumbria to Heysham in north Lancashire via a tunnel under Morecambe Bay.
The tunnel would be for cables only, with no vehicle access, and could cost up to £3bn.
This plan would also include a line of 46m-high pylons, running from Carlisle south to Whitehaven and on to Barrow.
National Grid will begin consulting on its proposals in September.
Construction work would not start until the next decade.
Other options National Grid has looked at include new cables across south Cumbria from west to east, and an offshore route which would extend into the Irish Sea before coming back on land at Heysham. However, it said both these involved “significant practical, environmental and technical challenges”.
National Grid’s project manager Robert Powell said: “The discussions we’ve had over the course of several years have given us invaluable information which has helped us develop and refine the options for connecting new power generation into our network.
“We’re now at a crucial stage of our project. We’re getting ready to share with local communities all the work that we have done to date and to seek their views on our findings including what we have identified as our ‘emerging preference’ at this point.
“We promise to listen, to learn from what we hear and then to seek to develop the project in a way which achieves a balance between meeting our country’s future energy needs and protecting the very special landscapes it touches upon.”