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19 June 2025

Ensuring grid stability in the renewable energy era

As Europe advances towards climate-neutral power systems, system stability becomes a central focus of policy and regulation. In the context of the Iberian blackout discussion, an Agora analysis shows that stronger interconnection is key for a resilient European electricity system.

Ensuring grid stability in the renewable energy era

Update 4 Juy 2025: This article has been revised to provide more information about the causes of the Iberian blackout and to reflect changes made to the slidedeck publication.

The recent blackout on the Iberian Peninsula put a spotlight on the resilience of Europe’s electricity systems. Initial findings by the Spanish government into its cause showed a combination of factors, including conventional power plants not responding as planned. It has also become clear that renewable energy could have contributed to system stability but was limited by regulatory and operational gaps. Contrary to initial speculation following the incident, the Spanish grid operator furthermore confirmed that the cause was not a lack of inertia. Instead, growing voltage instability triggered a cascade of generator disconnections ultimately leading to a system collapse. 

While further investigations are still ongoing, the incident highlights the need to accelerate infrastructure buildout as well as regulatory and policy adaptations to secure system resilience on the way to a climate-neutral European energy system.

A new Agora analysis outlines recommendations for grid stability in increasingly renewables-based power systems where inverter-based resources such as wind, solar and battery storage play a key role. The analysis draws on a recent Agora publication and includes a detailed reconstruction of the blackout based on publicly available information, including from the Spanish government and the European energy regulator ENTSO-E. 

Matching grid expansion and improved planning is key. 

A key area demanding attention is the development and reinforcement of grid infrastructure. Greater interconnection between the Iberian Peninsula and the broader European grid, for instance, could have mitigated the blackout’s impact – provided sufficient coordination among transmission system operators. 

Infrastructure expansion alone, however, is not enough; it must be matched by planning processes and regulatory frameworks that facilitate the rapid deployment of grid stability solutions, enable smarter grid operations and enhance system flexibility.

To this end, a transparent quantification of system stability needs, and optimal sourcing of relevant services will be essential. Countries such as the United Kingdom have already undertaken system-wide inertia assessments, while fast-response service procurement in places like Texas and Australia offers replicable models. 

Within the European Union, the ongoing revision of the network code presents an opportunity to enshrine such principles. Embedding support for technologies such as grid-forming inverters - while balancing standardisation with appropriate remuneration - will be essential for securing long-term system stability.

From Ireland to South Australia, reliable power systems with high shares of renewables are already a reality

Experts and system operators have long recognised that Europe’s existing frameworks must evolve in parallel with the new generation mix. In Spain, many solar and wind power plants were technically capable of providing  voltage support, but in practice were not required to do so due to outdated connection rules and delayed enforcement of key standards. This limited their ability to contribute to system stability during the blackout and highlights the urgency of aligning operational rules with the realities of a  renewables-based power system. 

Successful examples around the world demonstrate that renewables-based power systems are both stable and reliable. Countries like Ireland and Denmark, as well as regions like South Australia, routinely operate with more than 70 percent of electricity supplied by variable renewable sources at any given time. They achieve this through the deployment of advanced grid services – such as fast frequency response, synthetic inertia and voltage support – which mimic the stabilising characteristics of traditional generators. These examples showcase the critical role of modern control technologies, supportive regulation and coordinated planning in enabling resilient clean energy systems.

The Iberian blackout serves as a call to action. The technologies and know-how required for a stable, renewables-powered future are already available. What is needed now is decisive policy action, regulatory clarity and infrastructure investment to deliver on Europe’s energy transition while securing reliability.

The slide-deck “Power system stability in the age of renewable energy - recommendations in the context of the Iberian blackout” is available for download below.

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