CMA Issues Final Determination Closing RWE's Appeal Against GEMA's Rejection of CUSC Modification
On 19 October 2026, the Competition and Markets Authority (CMA) issued its final determination and order in the appeal brought by companies within the RWE group against a decision by the Gas and Electricity Markets Authority (GEMA), the governing body of Ofgem, made on 1 May 2026. The appeal concerned GEMA's rejection of RWE's proposed modification to the Connection and Use of System Code (CUSC), which is the industry code governing how generators and suppliers connect to and use the electricity transmission system in Great Britain. The RWE appellants were Gwynt y Mor Offshore Wind Farm Limited, RWE Renewables UK Limited, and RWE Renewables UK Swindon Limited. RWE sought permission to appeal on 26 May 2026; the CMA granted permission on 9 June 2026 and appointed a panel of three members chaired by Kirsten Baker CBE, alongside Roland Green and Frances McLeman, to determine the appeal. Main hearings took place on 9 September 2026. The CMA published its determination and order on 19 October 2026, closing the case. The sources confirm the determination was published but do not describe the outcome of the appeal or what the determination decided.
Why this matters
Energy code modification appeals to the CMA are a specialist and high-stakes area of regulatory law: CUSC modifications directly affect the revenue recovery mechanisms and grid connection rights of generators, and an adverse GEMA decision can have material financial consequences for large renewables operators like RWE. The CMA's role as appellate body for GEMA decisions under the energy regulatory framework means its determination sets a precedent for how future code modification disputes are resolved. Given the RWE appellants included offshore wind and onshore renewables entities, the outcome has potential relevance for how the renewables sector can challenge Ofgem decisions as the UK accelerates its clean energy buildout.
On the Ground
This type of regulatory appeal activates energy regulatory law, administrative law, and specialist dispute resolution practices. Solicitors advising energy generators on CUSC modification disputes must navigate the specialist procedural rules governing CMA regulatory appeals, prepare detailed technical and legal submissions, and manage the interface between technical industry-code arguments and legal grounds of challenge. No advisers are named in the sources. A trainee on this matter would be preparing chronologies of the CMA's administrative timetable, indexing written submissions, summarising GEMA's response to the notice of appeal, and assisting with court-bundle pagination for the main hearings.
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“What is the CMA's role in energy code modification appeals, and why would a renewables company like RWE challenge GEMA's decision to reject a proposed CUSC modification?”
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