CMP463: Stabilising the Specific Onshore Expansion Factors from 1st April 2026
What is being proposed
The Price Control from April 2026 has led to large, unexpected increases in Specific Onshore Expansion Factors. This modification seeks to hold those Specific Expansion Factors at 2025/26 levels, similar to the CMP353 approach, ahead of a larger more fundamental review of TNUoS.
Current status
Proposal raised on 31 October 2025 requesting urgency. A Special CUSC Panel was held on 14 November 2025. The Panel unanimously agreed that CMP463 met the Authority’s Urgency criteria (a) and therefore recommended urgent treatment. Panel’s recommendation was sent on 14 November 2025 seeking an Authority decision by 5pm on 21 November 2025. The Panel recommended that CMP463 proceed to Code Administrator Consultation. On 19 November 2025 the Authority approved the urgency timeline. The Code Administator Consultation opened on 21 November - 25 November. The Final Modification Report will be presented to the CUSC Panel on 12 December 2025. (05.01.2026) The Final Modification Report was sent to the Authority on 12 December 2025. (05/02/2026) On 27 January 2026 the Authority approved CMP463 and directed this modification be implemneted on 01 April 2026.
Details
Timeline
Analysis
Ofgem approved CMP463, freezing Specific Onshore Expansion Factors at 2025/26 levels from 1 April 2026. The modification prevents large unexpected increases in these TNUoS charges that would have resulted from the 2026 Price Control. The freeze is temporary, pending a fundamental TNUoS review.
Why it matters
This is parameter adjustment to prevent shock increases in transmission charges, not structural reform of the broken TNUoS methodology. Generators avoid higher charges temporarily, but the underlying problem — volatile charging factors that shift costs unpredictably — remains unaddressed until the promised fundamental review.
Key facts
- •Approved 27 January 2026, effective 1 April 2026
- •Freezes Specific Onshore Expansion Factors at 2025/26 levels
- •Prevents increases caused by 2026 Price Control
- •Temporary measure pending fundamental TNUoS review
- •Follows similar CMP353 approach