Ofgem Publishes RIIO-T3 Final Determination for National Grid

TL;DR

Ofgem dropped the RIIO-T3 final decision for National Grid's transmission network, setting revenue for 2026-2031.

AI Summary

National Grid plc announced on December 4, 2025, that the UK's energy regulator, Ofgem, has published its RIIO-T3 final determination. This determination sets the allowed revenue for National Grid Electricity Transmission (NGET) for the period from April 1, 2026, to March 31, 2031. The final determination is a crucial step in the price control process for the transmission network.

Why It Matters

This regulatory decision directly impacts National Grid's future revenue and investment plans for its electricity transmission network in Great Britain, influencing the cost of energy for consumers.

Risk Assessment

Risk Level: medium — Regulatory decisions can significantly impact a company's financial performance and future investment strategies.

Key Players & Entities

• National Grid plc (company) — Registrant
• Ofgem (company) — UK energy regulator
• RIIO-T3 (regulation) — Price control framework
• National Grid Electricity Transmission (NGET) (company) — Transmission business
• April 1, 2026, to March 31, 2031 (date_range) — Period covered by the determination
• December 4, 2025 (date) — Date of announcement

FAQ

Filing Documents

• a2463k.htm (6-K) — 35KB
• 0001654954-25-013665.txt ( ) — 37KB

From the Filing

'S RIIO-T3 FINAL DETERMINATION PUBLISHED a2463k     UNITED STATES   SECURITIES AND EXCHANGE COMMISSION Washington D.C. 20549     FORM 6-K     REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934   Date: 04 December 2025   Commission File Number: 001-14958     NATIONAL GRID plc   (Translation of registrant’s name into English)   England and Wales   (Jurisdiction of Incorporation)      1-3 Strand, London, WC2N 5EH, United Kingdom (Address of principal executive office)       Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.   ☒   Form 20-F       ☐   Form 40-F   Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):   ☐   Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):   ☐   Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3- 2(b) under the Securities Exchange Act of 1934.   ☐   Yes     ☒   No   If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): n/a       EXHIBIT INDEX   Exhibit No.     Description     99.1   Exhibit 99.1 Announcement sent to the London Stock Exchange on 04 December 2025   — Ofgem's RIIO-T3 Final Determination published     Exhibit 99.1     4 December 2025   National Grid plc   Ofgem's RIIO-T3 Final Determination published     Ofgem has today published its Final Determination for the RIIO-T3 framework covering our National Grid Electricity Transmission business for the period April 2026 to March 2031. The proposals include a real allowed cost of equity of 6.12% at 60% gearing.   We welcome Ofgem's recognition of the need for significant investment into the electricity transmission sector to continue to deliver world leading reliability whilst nearly doubling the amount of power we can transfer around the country.   We will now review in detail the full package contained within the Final Determination, to assess how Ofgem have addressed the critical points we raised in our Draft Determination response, and therefore whether it delivers an overall framework that is both investable and workable. This includes an incentive framework that allows high performing networks to achieve a globally competitive overall return and totex mechanisms that enable transmission owners to recover the efficient cost of their investments whilst progressing projects at the pace expected by our stakeholders.   We expect Ofgem to publish the proposed licence modifications for consultation soon. These important documents will inform our assessment of the incentive opportunities and overall workability of the framework. Throughout this period we will continue to work closely with Ofgem ahead of publication of its decision on the licence in February. Relevant parties will then have 20 working days to assess the licence modifications. We anticipate announcing our response in early March 2026.     Enquiries and contacts   Investors and Analysts   Angela Broad   +44 (0) 7825 351 918   Tom Edwards   +44 (0) 7976 962 791   Cerys Reece   +44 (0) 7860 382 264       Media   Alex Roache   +44 (0) 7843 802 006   Ben Davis   +44 (0) 7914 539 999   Dan Roberts, Brunswick   +44 (0) 207 404 5959         Cautionary statement   This announcement contains certain statements that are neither reported financial results nor other historical information. These Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These Company) financial condition, its results of operations and businesses, strategy, plans and objectives. Words such as 'aims', 'anticipates', 'expects', 'should', 'intends', 'plans', 'believes', 'outlook', 'seeks', 'estimates', 'targets', 'may', 'will', 'continue', 'project' and similar expressions, as well as and climate-related risks which differ from conventional financial risks in that they are complex, novel and tend to involve pro

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View this 6-K filing on SEC EDGAR