In 2011, National Grid commissioned a report from the independent research institute IET (Institution of Energy and Technology). The report analyses the lifetime costs of installing and maintaining different high voltage electricity transmission connection options - for example, overhead lines, underground cables and subsea high voltage direct current (HVDC). The report comes to the conclusion that there are significant cost differences between the available options.
In 2010/11, National Grid carried out a public consultation on a new approach to undergrounding. After producing a draft of the approach, National Grid asked people for their views on the document and revised it according to the feedback received. For the consultation, National Grid informed the public via media, set up a consultation website and online questionnaire, organised five workshops (each with some 20 participants), and held a number of individual meetings with interested parties. The findings of this consultation are published in a consultation report on National Grid’s website. The final approach is published in a brochure and on a factsheet. National Grid considers every case for using underground cables on its own merits. In view of the additional costs, undergrounding will only be a solution in very restricted circumstances. They are considered in exceptionally constrained urban and rural areas or for major river crossings.
In 2015, National Grid produced a holistic report on the topic, entitled "Undergrounding high voltage electricity transmission lines". This aims to give an overview of the topic and also explains the technical issues behind insultation, installation costs, underground cable technologies, environmental issues, land-use restrictions, operation, installation methods, components of undergrounding systems and EMFs.