Decision on 2019-20 Interest During Construction (IDC) rates for offshore transmission projects and cap and floor interconnectors

Publication date
30th May 2019
Information types
Policy areas

This letter sets out our decision on the specific Interest During Construction (IDC) rates that will apply to those offshore transmission projects and electricity interconnectors subject to the cap and floor regime that reach Final Investment Decision (FID) during 2019-20.


  • Offshore transmission IDC: we  decided to set the IDC cap rate at 7.08% (pre-tax, nominal) for those offshore transmission projects reaching FID during 2019-20.
  • Interconnector IDC: we decided to set the IDC rate at 3.12% (vanilla, real-RPI) for those cap and floor Window 2 interconnector projects reaching FID during 2019-20.