National Grid has said that the overall cost of the project is around £1bn and while it is always difficult to breakdown costs simply into different engineering elements, they have estimated the following:
Tunnels and associated mechanical and electrical work 50%
High voltage cable procurement, installation and testing 15%
Substation works (including civil ground works at these locations) 26%
Land and required permissions 9%
Ofgem is responsible for regulating National Grid, to ensure that the work they do represents value for money for consumers.