Question to the Department for Energy Security & Net Zero:

To ask the Secretary of State for Energy Security and Net Zero, what comparative estimate his Department has made of the costs of transmitting energy by (a) undersea cables and (b) pylon networks.

The Department has not conducted its own assessment of the comparative costs of undersea cables and pylon networks. However, in April 2025, the Institution of Engineering and Technology published average lifetime cost estimates which suggest that 400kV AC overhead lines cost approximately £1,190/Megawatt-kilometre (MWkm), while subsea HVDC connections between onshore substations cost around £6,170/MWkm—over 5.2 times more.