Network Imperfections Charges October 2026 – September 2027 and Reforecast Report October 2024 – September 2025 Decision Paper

Today, the Regulatory Authorities (RAs) publish a decision paper setting the network imperfections charge for the all-island Single Electricity Market (SEM) for the period October 2026 to September 2027.

Network imperfections costs arise when the electricity network cannot fully deliver market outcomes due to physical constraints on the transmission system. These costs are incurred by the Transmission System Operators (TSOs), SONI and EirGrid, as they manage the secure and reliable operation of the electricity system. Such costs are a normal feature of electricity markets and have been increasing across Europe because of higher fuel prices, particularly gas, and the growing complexity of integrating larger volumes of renewable generation.

The purpose of the Network Imperfections Charge is to allow the TSOs to recover the costs of managing these constraints and maintaining system security. As the charge is based on forecasts, it includes a K-Factor adjustment that accounts for differences between forecast and actual costs from previous years.

The SEM Committee has approved a slightly lower network imperfections charge than proposed, of €793.23 million for 2026/27, equivalent to an estimated imperfections price of €18.81/MWh. This is €3.6 million lower than the TSOs’ proposed charge of €796.92 million (€18.90/MWh).

Compared with the 2025/26 approved costs, the decision is expected to place downward pressure on consumer electricity bills, assuming suppliers pass on the full benefit. The estimated annual impact is: 
•    £3.07 reduction for customers in Northern Ireland. 
•    €4.69 reduction for customers in Ireland.

While some cost drivers, such as international fuel prices, remain outside the control of regulators and system operators, the SEM Committee and TSOs are continuing to implement a broad programme of work to reduce manageable costs. This includes measures to improve system operations, support the efficient integration of renewable energy, and address the underlying drivers of network imperfections costs.

The decision paper also considers responses received to the earlier consultation (SEM-26-29), which were reviewed before final decisions were made.

For further information please contact the Market Modelling Group (mmg@cru.ie ) and the All-Island Regulation Team (tsc@uregni.gov.uk ).