Energy Explained: Future-Proofing GB’s Power System: Reflections on the April 2025 Iberian Event

The Impact of the Iberian Blackout

The blackout in Spain and Portugal earlier this year showed just how devastating a power failure can be. On April 28, parts of the Iberian Peninsula were without power for up to 19 hours. This sudden loss of electricity left many homes, businesses, and essential services without power or relying on back-up supplies and must have been a frightening experience. This event highlights the critical importance of having a reliable and resilient energy system.

NESO’s Responsibility and Approach

As the National Energy System Operator (NESO) for Great Britain (GB), ensuring a safe and secure electricity supply is at the heart of everything we do. NESO has a responsibility to learn from major incidents that happen elsewhere. Even though GB has one of the most reliable networks in the world – a record NESO, network operators, and the whole energy industry work tirelessly to maintain – exploring every opportunity for learning and improvement is essential. NESO would be guilty of complacency if we did not reflect on what happened in April, even though the GB network was unaffected.

The Technical Assessment Report

NESO has produced a report, Future-Proofing GB’s Power System: Reflections on the April 2025 Iberian Event, which examines what lessons can be applied to GB. The purpose of the report is not to draw conclusions or comment on the Iberian incident itself. We trust and await the factual and final reports from ENTSO-E, who are leading the investigation and will inform broader European grid resilience efforts. Our report has been produced as part of NESO’s drive for continuous improvement and to see how we can make our system even more resilient.

Resilience Measures in GB

As the report explains, NESO has worked with the GB energy sector to implement rigorous planning, testing, monitoring, and control measures to ensure the resilience of our power system. These measures include mitigation's to prevent the issues that affected the Portuguese and Spanish energy systems. GB’s energy system is well-protected against the sequence of events that led to April’s blackout, and our experts are working day and night to ensure nothing of that nature happens here. Our report looks at the various factors which led to the blackout and compares these with the situation in GB. In short, the report finds that NESO has taken action to mitigate many of the risks seen in Iberia and must continue to build on existing planning, testing, and system monitoring capabilities, particularly in voltage management. Our ongoing stability pathfinder procurement will increase resilience further.

Next Steps for GB’s Power System

Other steps to be taken include monitoring, data and asset availability from Transmission Owners (TOs), and driving improvements. Resilient communications between control centres, real-time data, and coordination between system operators and network owners must be prioritised. NESO’s report explores these findings and other issues in far more detail.

NESO's Report

NESO’s 12-page report explores these findings and other issues in far more detail. Another example of our determination to enhance GB’s energy security and of our drive for improvement.

Craig Dyke, Director of System Operations, NESO

Read the report