Volume of energy not supplied: Electricity transmission (RIIO-T1)


Source: RIIO electricity transmission annual report 2017-18.

Information correct as of: March 2019

This chart is an indicator of company performance on reliability and availability of energy. It shows the volume of electricity not supplied by electricity transmission owners. ‘Energy not supplied’ means the volume of energy to customers that is lost as a result of faults or failures on the network.

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.

Policy Areas:

  • Electricity - transmission

Data Table

Volume of energy not supplied: Electricity transmission (RIIO-T1)
Year 1 actualYear 1 targetYear 2 actualYear 2 targetYear 3 actualYear 3 targetYear 4 actualYear 4 targetYear 5 actualYear 5 target
National Grid Electricity Transmission1353168.73164.53166.831639.7316
Scottish Power Transmission42.22252.822513.922510.32253225
Scottish Hydro Electricity Transmission35.6120106.112001204.412024.3120

More information

Volume of energy not supplied: At-a-glance summary

  • All three transmission operators have significantly outperformed their targets in year five (2017-18) of the RIIO-T1 price control.

Relevance and further information

  • Ofgem sets targets for each transmission owners’ level of energy not supplied.
  • Under the price control, we expect companies to maintain network reliability and reduce the number and duration of power cuts.


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