OFTO projects and cap and floor interconnectors: Interest During Construction (IDC) rates for 2026 to 2027
- Publication type:
- Decision
- Publication date:
- Topic:
- Offshore electricity transmission,
- Electricity interconnectors
Our decision on updated IDC rates for 2026 to 2027 which will apply to offshore electricity transmission (OFTO) projects and electricity interconnectors granted the cap and floor regime.
Details
This letter sets out our decision on the updated IDC rates for OFTO projects and Window 3 cap and floor electricity interconnectors to apply to projects taking Final Investment Decision (FID) in 2026 to 2027.
Based on this updated methodology and a reference date of 31 January 2026, we have decided that:
- for OFTO projects, we will set the IDC rate capped at 9.55% (pre-tax, nominal) for projects reaching FID in 2026 to 2027 (9.74% in 2025 to 2026)
- for Window 3 interconnectors, we will set the IDC rate at 5.49% (vanilla, real-CPIH) for projects reaching FID in 2026-27 (5.37% in 2025 to 2026)
'Vanilla' is the most basic or standard form of an asset or financial instrument. CPIH is the Consumer Prices Index including owner occupiers' housing costs.
The IDC rate for any outstanding Window 1 project will be set after the project’s FID date in accordance with our policy. For any outstanding Window 2 projects, the IDC rate will be determined once the project has reached FID. This will follow the methodology detailed in the 2023 to 2024 IDC decision letter.