The NESO report examines what lessons can be learnt from the 28 April power outage in Spain and Portugal and applied to the UK grid. Working with the energy sector, NESO says it has implemented rigorous planning, testing, monitoring and control measures to ensure the resilience of the UK grid and has mitigated many of the risks seen in the Iberian blackout. However, additional planning, testing and system monitoring capabilities are needed, particularly in voltage management, it says.

Noting that the purpose of its report is ‘not to draw conclusions or comment on the Iberian incident itself’, NESO says published findings to date suggest the blackout was caused by a series of separate incidents whose effects accumulated and led to a system overvoltage which triggered a cascading shutdown of generation.  

Three main lessons have emerged from studies of the incident – the need to manage current oscillations, control voltage and have coordinated restoration plans.

Addressing each in turn, NESO says the Iberian power outage ‘highlights the importance of understanding, monitoring and reducing oscillations through modelling, simulations, testing and compliance’. It reports that new measurement tools that can identify the presence of oscillations are monitoring the UK’s electricity grid. It is also working with transmission operators to ‘prioritise installation of further phasor measurement units’ (PMUs – devices to monitor the network at chosen locations and help with oscillation identification) which will ‘provide additional capability to monitor and measure oscillations at a national and local level’ in real time.

Moving to voltage instability – reported to be a key contributing factor to the Iberian power outage – NESO explains that the UK already ‘requires reactive capability and voltage control from all generation plants, including non-synchronous renewables’, which is periodically tested. It adds that ‘new reactive power markets to procure additional voltage regulation services through competition’ have been developed in the UK, which should ‘improve the voltage situation significantly in the short to medium term’. Modelling is an ‘area for improvement in medium to long term timescales for both NESO and the transmission owners’, continues NESO. ‘For example, modelling could be improved to account of market sensitivities and asset availability.’

Lastly, NESO points out that electricity system restoration in the UK is currently carried out using a designated fleet of power stations and interconnectors that are contracted for restoration services. However, to ensure the capability to restore what is a rapidly evolving generation landscape is maintained, NESO says it has ‘adapted its restoration contracting strategy to include a range of new technologies both at transmission and distribution level’.

Under a new Electricity System Restoration Standard (ESRS), NESO is required to have sufficient capability and arrangements in place no later than 31 December 2026 to restore 100% of the country’s electricity demand within five days. This requirement must also be implemented at a regional level, with an interim target of 60% of regional demand to be restored within 24 hours.  

Shortly after NESO published its report, the European Network of Transmission System Operators for Electricity (ENTSO-E) published its factual report presenting facts and data on the system conditions during the Iberian blackout, as well as a detailed sequence of events. The report does not analyse the root causes of the blackout. A further ENTSO-E report is expected in 1Q2026, which will include an in-depth analysis of the events of 28 April, establish the root causes of the incident, and include recommendations for improving the resilience of the European power system.

In a joint statement on the ENTSO-E report, SolarPower Europe, the Spanish PV association (UNEF) and the Portuguese renewables association (APREN) said: ‘The Iberian blackout must be a moment of learning.’ They also reiterated their call for ‘accelerated investment in grid resilience, stability and system flexibility – especially by allowing renewables to provide dynamic voltage control, and facilitating the integration of battery storage and grid-forming inverters’. They added: ‘These technologies are already available and should be procured to further support stable voltage levels, managing variability, and delivering renewable-powered energy security.’

NESO unveils timeline to accelerate clean energy grid connections

Meanwhile, NESO has set out a new timeline for the connections reform process. The updated timeline comes after the regulator Ofgem identified delays in grid connections as a critical bottleneck for clean energy projects such as solar farms and battery energy storage systems (BESS).

From December 2025, NESO plans to start communicating the projects that have been successful in securing a place in the reformed connections queue. Projects that are due to connect in 2026 and 2027 will be prioritised. NESO will begin delivering the 2030 and 2035 offers next year.  

First statistics on progress to clean power by 2030  

In related news, RenewableUK reports that new government figures show that 73.8% of UK electricity generation in 2024 came from clean power sources (renewables and nuclear), up from 68.3% in 2023.

It is the first time that official statistics on progress towards the government’s clean power by 2030 goal have been published.  

The report also shows that the percentage of electricity generated by renewables in April to June this year hit a new quarterly record of 54.5%, up from 51.7% in 2Q2024.

Offshore wind increased by 10% and solar by 27%, due to more capacity and record sun hours, according to the report.

Low carbon sources also set a new record of 69.8% of electricity generation, up from the previous record of 69.3% set in the same quarter last year.

Meanwhile fossil fuels dropped to a record low of 26.7%, with wind outpacing gas for the third time in a quarterly period.

Commenting on the statistics, RenewableUK’s Director of Future Electricity Systems Barnaby Wharton says: ‘It’s great to see that Britain is making excellent progress towards clean power by 2030, with a significant increase in 2024 compared to the year before, as we roll out vital new wind and solar projects, strengthening our capacity to generate secure homegrown power. This will insulate bill payers in the long term against the volatility of international gas prices which caused the energy crisis.’