Sulphur Hexafluoride (SF6) emissions: Electricity transmission (RIIO-T1)


Source: RIIO electricity transmission annual report 2017-18.

Information correct as of: March 2019

This chart is an indicator of environmental impact. It shows company performance against an emissions reduction target electricity transmission owners must deliver for consumers under RIIO-T1.

 We update this chart on an annual basis. Click the ‘more information’ tab above for a summary of the latest trends, details of how to interpret the figures and for information on methodology.

Please note: NGET’s historic SF6 loss figures have been adjusted in line with a 2017 revision Methodology Statement in Respect of SF6 Gas Leakage.

Policy Areas:

  • Electricity - transmission

Data Table

Sulphur Hexafluoride (SF6) emissions: Electricity transmission (RIIO-T1)
Y1 Actual emissionsY1 Target emissionsY2 Actual emissionsY2 Target emissionsY3 Actual emissionsY3 Target emissionsY4 Actual emissionsY4 Target emissionsY5 Actual emissionsY5 Target emissions

More information

Sulphur Hexafluoride (SF6) emissions: At-a-glance summary

  • In 17/18 all three transmission operators outperformed against their target emissions levels of SF6. 
  • Scottish Hydro Electricity  Transmission's leakage rate is, again above the target figure and will therefore be penalised under the incentive mechanism, although the level is marginal. 
  • Scottish Hydro Electricity  Transmission and Scottish Power Transmission reported a reduction in SF6 leakage from the previous year. 

Relevance and further information

  • SF6 is an extremely effective electrical insulator and so is used in high-voltage switchgear and other electrical equipment. It is also a potent greenhouse gas.
  • Electricity transmission owners are incentivised to limit their emissions of SF6. Ofgem target levels of emissions that we expect companies to beat. 


Each year, network companies must report on their performance under the RIIO-T1 price control. Our review of their submissions and supporting information informs our annual publications on network company performance.

Date correct
March 2019
Policy area