UK–EU ELECTRICITY TRADING AGREEMENT FRAMEWORKS

Introduction

UK–EU electricity trading is governed by a post-Brexit combination of international agreements, domestic energy regulation, interconnector arrangements and continuing cooperation between system operators and regulators. Since 1 January 2021, Great Britain has operated outside the EU Internal Electricity Market and no longer participates automatically in EU market-coupling mechanisms. Electricity nevertheless continues to move between Great Britain and neighbouring European markets through interconnectors. The central legal framework is the EU–UK Trade and Cooperation Agreement (TCA), supplemented by technical arrangements, regulatory cooperation and special rules for Northern Ireland.

Trade and Cooperation Agreement

The TCA contains a dedicated energy framework dealing with electricity and gas markets, network access, security of supply, offshore energy, infrastructure planning and efficient use of interconnectors. It requires cooperation between UK transmission system operators and European bodies, including arrangements involving ENTSO-E and relevant regulators.

A principal objective is to establish efficient electricity trading over interconnectors while maintaining separate UK and EU electricity markets. After Brexit, Great Britain ceased participating directly in the EU’s Single Day-Ahead Coupling and Single Intraday Coupling arrangements. Consequently, interconnector capacity and electricity have generally been traded through alternative arrangements, which may be less efficient than integrated market coupling.

Interconnector Capacity Allocation

Electricity interconnectors physically connect Great Britain with European markets including France, Belgium, the Netherlands, Ireland and Denmark. Their operation involves allocation of transmission capacity, congestion management, balancing and coordination between transmission system operators.

The TCA contemplated development of a system known as multi-region loose volume coupling (MRLVC). However, following technical work, UK and EU transmission system operators concluded in 2025 that the proposed MRLVC concept could not be validated in its contemplated form.

This illustrates that UK–EU electricity trading remains an evolving regulatory field rather than a fully integrated replacement for pre-Brexit market coupling.

Regulatory Cooperation

Ofgem plays an important role in cross-border electricity regulation alongside the Agency for the Cooperation of Energy Regulators (ACER) and national European regulators. Cooperation covers market operation, interconnector access, security of supply and infrastructure development. UK policy recognises that efficient cross-border markets can lower system costs, strengthen resilience and facilitate renewable-energy integration.

Northern Ireland and the Single Electricity Market

Northern Ireland occupies a distinct legal position. The Single Electricity Market (SEM) covering Northern Ireland and Ireland continues under arrangements connected with the Withdrawal Agreement. Relevant EU electricity rules therefore continue to apply in Northern Ireland to the extent necessary for the SEM’s operation.

Future UK Participation in the EU Electricity Market

The framework may change substantially. Following exploratory discussions concluded in 2025, negotiations began in May 2026 concerning possible UK participation in the EU Internal Electricity Market. The proposed arrangements contemplate closer integration of wholesale and retail electricity markets, trading platforms and relevant EU energy institutions.

CASE LAW

Case Name/Citation

ACER v Aquind Ltd, Case C-46/21 P, EU:C:2023:182

Facts

Aquind proposed an electricity interconnector between Great Britain and France and requested an exemption from certain EU rules governing new interconnectors. UK and French regulators failed to agree, causing the matter to be determined by ACER. ACER rejected the exemption application.

Legal Issue

The issue concerned the extent of ACER’s regulatory discretion and the intensity of review required from its Board of Appeal when deciding disputes involving cross-border electricity infrastructure.

Judgment

The Court of Justice upheld the requirement that ACER’s Board of Appeal conduct a sufficiently complete review of technically complex regulatory decisions.

Legal Principle/Ratio

Cross-border electricity regulation must remain subject to effective administrative and judicial scrutiny even where regulators exercise specialised technical expertise.

Significance

The case demonstrates the legal complexity of UK–EU interconnectors and the continuing relevance of EU regulatory law to infrastructure linking Britain with European electricity markets.

Case Name/Citation

Tempus Energy Ltd v European Commission, Case T-793/14

Facts

Tempus Energy challenged the European Commission’s approval of the UK Capacity Market, arguing that demand-side response was disadvantaged compared with electricity generation.

Legal Issue

Whether the Commission had sufficiently investigated the compatibility of the UK scheme with EU State-aid rules.

Judgment

The General Court initially annulled the Commission decision because a formal investigation should have been undertaken; that ruling was subsequently overturned by the Court of Justice in Commission v Tempus Energy, Case C-57/19 P.

Legal Principle/Ratio

National electricity-market mechanisms interacting with cross-border competition may be subject to detailed supranational legal scrutiny where EU law applies.

Significance

The litigation illustrates how electricity security, market design and competition regulation became closely interconnected under the UK’s former participation in the EU electricity framework and remain relevant when designing future UK–EU arrangements.

Conclusion

UK–EU electricity trading now operates through the TCA, interconnector agreements, regulatory cooperation and specialised arrangements for Northern Ireland. The framework seeks efficient trade and security of supply while recognising that Great Britain and the EU presently operate separate markets. Ongoing negotiations begun in 2026 could lead to substantially closer electricity-market integration and potentially reshape the legal architecture of cross-border electricity trading.