What we know – and don’t – about the April 2025 Iberian Peninsula Power Blackout

As the recent Iberian Peninsula power blackout underscored, ensuring that electricity grids are modern, resilient, and flexible is essential, whether here in the U.S. or abroad. As the clean energy transition continues to unfold, SEPA is increasingly focused on leveraging global insights to enable U.S. industry leaders to stay agile and informed, fostering collaboration and learning across the global energy ecosystem.

Q&A

What happened with the power grid in Spain, Portugal, and parts of France on April 28, 2025?

During the early afternoon of Monday, April 28, 2025, the power grid in Spain experienced a cascading event and lost about 60% of its power generation. The sudden 15 gigawatt loss in electricity generation impacted grid frequencies and stability across the integrated Iberian Peninsula grid, leading to a nearly daylong blackout across Spain, Portugal, and parts of southern France. By late Monday evening, Redes Energéticas Nacionais (REN), Portugal’s national electricity and natural gas transmission system operator, had restored 85 of 89 substations in Portugal. Red Eléctrica de España (REE, “Red Eléctrica”), Spain’s national electricity transmission system operator, had restored nearly all demand in Spain by Tuesday morning.

What caused the power grid failure in Europe? (Spoiler: We don’t know yet.)

Understanding the triggers behind a blackout across a large, integrated, diverse network is complicated.

The official causes of the April 2025 power grid failure in Spain, Portugal, and parts of southern France are under investigation. The Spanish government has established a national investigation committee, the European Union’s Agency for the Cooperation of Energy Regulators announced an independent audit (at Portugal’s request), and other investigations are underway. This is similar to the investigation process that occurred following the 2003 blackout in the United States and the subsequent U.S.-Canada Power System Outage Task Force and report.

While official reports are forthcoming, in initial press statements, the Spanish government and Red Eléctrica emphasized that the power outage was not due to renewable energy generation because the system has “worked to perfection with a similar demand situation and with a similar [electric generation] mix” and also ruled out a cyberattack. [1]

However, as sources including the European Network of Transmission System Operators for Electricity (ENTSO-E) have highlighted, the electrical inertia profiles and responses of different generation resources that are part of the grid mix are a key factor in stabilizing grid frequency and voltage during sudden fluctuations or imbalances. Inverter-based resources like solar and wind provide limited frequency regulation compared to other generation (e.g., hydropower, nuclear, natural gas) if not paired with advanced inverters that provide grid-support functions such as synthetic inertia and voltage regulation.

As additional data emerges on the grid conditions at the time of the event, U.S. energy industry stakeholders can learn from recent challenges and leverage future recommendations.

How does the power system in this part of Europe compare to the United States? Do they have the same or similar standards for preventing blackouts?

Spain, Portugal, and the U.S. each operate advanced and highly coordinated power systems, but their structures differ in key ways that affect how they plan for and respond to outages. See Table 1 for an in-depth comparison of the planning, operations, and reliability standards of the power systems in the U.S., Spain, and Portugal.

Spain and Portugal each have a single national transmission operator and balancing authority—REE and REN—while the U.S. grid is divided into dozens of balancing authorities and local balancing areas, coordinated by multiple transmission system operators or utilities depending on location. In the U.S., the North American Electric Reliability Corporation (NERC) develops mandatory reliability standards, and the Federal Energy Regulatory Commission (FERC) provides enforcement. [2] In contrast, Spain and Portugal follow EU-wide standards set by the European Network of Transmission System Operators for Electricity (ENTSO-E), which are legally binding across the EU. [3]

Both systems aim to ensure reliability, but differences in governance, planning, and enforcement shape how each responds to grid events like the April 28th blackout. By effectively breaking down Spain and Portugal’s power system structures and systems as it relates to planning, operations and governance, U.S. energy stakeholders can draw comparisons on how we can learn and apply lessons from this event.

The grid is old, both in Europe and here in the United States. Are all these new technologies straining the system?

Not inherently. Inverter-based resources (e.g., wind, solar, and battery storage) and distributed energy resources (DERs) can strengthen the grid when planned and coordinated effectively. Without proper integration, they can create challenges, like voltage fluctuations, reduced visibility, and operational uncertainty. Investigators of the recent Iberian Peninsula blackout will be delving into issues of a lack of coordinated system planning, systems integration, and response that can lead to grid instability.

Both the U.S. and Europe are modernizing how they plan and operate the grid. In both systems, transmission and distribution operators play an active role in planning. The EU uses a Ten-Year Network Development Plan (TYNDP) coordinated across 36 European countries, while many U.S. utilities conduct integrated resource plans (IRP) and distribution system plans (DSP). As more distributed and intermittent resources connect to the grid, stronger coordination between transmission and distribution planning is needed to ensure reliable and resilient operations.

Deploying enabling technologies for these resources, such as advanced inverters, distributed energy resource management systems (DERMS), and grid-forming inverters allow grid operators to use DERs to support voltage, frequency, and peak load—turning them into grid assets rather than risks. [4]

The technologies are capable – the challenge is system-wide coordination.

Check out SEPA Resources: Decoding DERMS: Options for the Future of DER Management

What else is happening around the United States to improve system reliability?

The U.S. power system is very reliable – according to the U.S. Energy Information Administration, the average customer experiences less than two hours of power outages each year. Reliability refers to keeping the lights on consistently and without interruption.

For U.S. utilities, maintaining reliability alongside safety and affordability is the main objective. In order to meet that objective, utilities regularly evaluate their systems through annual DSPs, IRPs, and grid modernization proceedings to identify investments to improve system reliability. [5] These investments include traditional reliability improvements, like replacing poles and wires, improving redundancy, and upgrading substations, and next generation solutions, such as virtual power plants (VPPs), microgrids, and DERMs to improve system reliability and flexibility.

There are also efforts in the U.S. to establish new frameworks and redefine metrics and processes around system reliability and resilience. Tools like SEPA and NRECA’s Resilience Planning Playbook provide a framework and best practices for utilities to take a broader view of planning that includes evolving risks and community needs. Coordinated industry efforts, such as NERC’s working groups and industry strategies (e.g., Inverter-Based Resource Strategy and System Planning Impacts from Distributed Energy Resources Working Group) are also underway in the U.S. to increase focus on grid stability and improve system reliability.

Check out SEPA Resources:

• 50 States of Virtual Power Plants and Supporting Distributed Energy Resources: 2024 State Policy Snapshot
• SEPA and NRECA Resilience Planning Playbook for Electric Cooperative Utilities

What about the increasing frequency and severity of extreme weather? Does that increase the risk of blackouts here in the United States?

Similar to Europe, the U.S. is experiencing an increase in the frequency and severity of extreme weather. In 2024, the U.S. experienced 27 weather and climate disaster events with losses exceeding $1 billion each, and billion-dollar events have impacted all 50 states in the last decade.

Having a reliable and resilient energy system – one that delivers power and can withstand and bounce back from events – is critical. The total cost of power outages to American businesses is around $150 billion every year, and storm-related outages alone cost the American economy between $20 billion and $55 billion annually.

On top of traditional reliability investments, electric utilities are investing in projects that aim to increase grid resilience and mitigate the impacts of extreme weather events, such as microgrid solutions for at-risk communities or leveraging and coordinating customer resources (e.g., electric vehicles, battery energy storage systems) to provide backup power. Critically, the adoption of resilience planning frameworks has also become more widely recognized nationwide. Between May 2022 and June 2024, 30 utilities filed one or more resilience plans covering 47 million customers and with the aim to improve grid resilience for roughly 130 million people (or 39% of the U.S. population), with many more utilities also incorporating resilience within other utility planning processes.

Check out SEPA resources:

• Case Study: Hurricane Helene – Hot Springs Microgrid
• Reimagining Resilience: A Framework for Integrating Customer-Sited and Grid-Scale DERs
• The Microgrid Playbook: Community Resilience for Natural Disasters
• The State of Bidirectional Charging in 2023

Wrap-up

While investigations continue in Europe, SEPA continues to work with our diverse membership towards a clean, affordable, and resilient energy grid here in the U.S., and to identify and share solutions to the biggest challenges facing utilities, their partners, and policymakers.

Want to dive deeper and learn on-the-ground? Join us on SEPA’s 2025 Executive Fact Finding Mission to Portugal (October 26-31).

Questions? For SEPA members, email our complimentary member research service, staffed by SEPA experts: [email protected]

Appendix

Detailed comparison of power systems in the U.S., Spain, and Portugal

Authors:

Jared Leader, Senior Director, Research and Industry Strategy, Resilience
Kate Strickland, Director, Strategic Projects
Yok Potts, Director, Research and Industry Strategy, Policy
Lesley Jantarasami, Vice President, Research and Industry Strategy