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New report compares electricity transmission technologies

29/04/2025

We (SP Energy Networks) are the transmission owner for the electricity transmission network in Central and Southern Scotland. We recently published our next Transmission Business Plan (RIIO-T3) which lays out our proposal to invest £10.6 billion in our transmission network from 2026 to 2031 – a key period in the journey to enabling Clean Power 2030 and Net Zero targets. 

A Comparrison of Electricity Transmission Technologies reportA new independent report by Mott Macdonald for the Institution of Engineering and Technology (IET) compares costs, environmental impacts, carbon intensity, technology readiness and delivery time for a range of electricity transmission technologies.  

Britian is about to embark on the biggest overhaul to the electricity transmission grid since its inception. The much-needed expansion of the electricity grid will allow green electricity to be used more effectively, and ultimately provide consumers with benefits such as greener, more secure electricity that is more affordable in the long term.  

The new report describes in detail a wide range of different options for getting more out of the existing transmission network and for adding capacity to it and demonstrates the cost of the different technologies.  

The report found that, compared to overhead lines; 

  • underground cables are, on average, around 4.5 times more expensive  

  • offshore high voltage direct current (HVDC) subsea cables are around 5 times more expensive  

  • an offshore HVDC network connecting multiple sites to the onshore grid is 11 times more expensive 

Alongside costs, the report emphasised the importance of considering each technology on its merits in each specific grid development context considering environmental impact, engineering challenges and local impacts.  

Supply chain bottlenecks reported, especially in cable manufacturing, affecting delivery times and creating a need for long-term relationships with providers. 

The report provides examples of deployment of key technologies to give specific amounts of capacity over specific distances, taking into account the effects of fixed costs and costs that depend on distance.  

To view the full report on IET’s website please click here.  A two-page infographic highlighting key facts has also been produced:

Infographic - A comparrison of electricity transmission technologies

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