What the Iberian Peninsula blackout teaches us about the renewable energy transformation.

On April 28, 2025, I was in Portugal. Just after noon a large-scale power outage across the Iberian Peninsula, affecting Spain, Portugal, and parts of France and Andorra, interrupted the normal flow of proceedings and generally ruined everyone’s day!

This event was one of the most significant blackouts in recent European history, disrupting daily life for millions. Official reports released in June 2025 confirm that an over-voltage surge in southern Spain set off the chain reaction, but I’ve been reflecting on network resilience and the impact of renewables since it happened. Even though we now know renewables weren’t to blame, despite the claims of climate-deniers, could today’s renewables mix still leave us exposed to shocks like this? Are we becoming more vulnerable to this type of event as the energy transition progresses? And what has to happen to make the future grid resilient?

What was most interesting was the immediate personal and societal impact, the almost complete severing of access to modern “essentials” brought about within minutes and lasting many hours. It was the scale and scope of the impact that really shocked me. Obviously, all the lights went out. But also, elevators stopped mid-journey, the cell-phone network collapsed, Wi-Fi disappeared, traffic lights went dark, and the trains stopped. Shops, restaurants, and bars closed, not because they couldn’t cook but because they could not accept electronic payments. And after a while it was incredible to see the worry and anxiety of people whose phones and laptops were running out of power (Those of us with a good old-fashioned printed book felt rightfully special at that point). Modern life rewound a few decades for a good 12 hours. It was a strangely philosophical experience observing how such a large-scale event impacted at a very local level.

It’s useful to understand the sequence of events that led to the Iberian grid collapse. Between 12:03 and 12:07 CEST, and again between 12:19 and 12:21 CEST, the European power grid experienced oscillations in voltage and frequency. The grid frequency in the Iberian Peninsula plunged below 48 Hz, triggering load-shedding protocols. Within seconds, AC lines between France and Spain also tripped, isolating the peninsula and, ten seconds later, bringing the entire Iberian grid down. Power restoration began immediately, with Portugal fully restored by midnight and Spain by 04:00 the next morning, impressive by any standard.

Early speculation ran wild, everything from space weather to hackers, but each theory fell away as data accumulated. The Spanish government report and an ENTSO-E technical review rule out cyber intrusion and single out inadequate voltage control support from large thermal units that were offline at the time.

Now that we’ve labelled the incident a textbook cascade, sparked by an over-voltage and worsened by too little synchronous generation, we should also admit the broader truth: the energy-transition timetable is out-running grid-modernization.

If we just compare investments, renewables in 2024 saw about $770 billion in investments globally, whilst the grid remained at its long-term and consistent circa $300 billion. If generation technology was not changing, then perhaps this ratio would be okay. But as we replace large spinning masses that are hard to slow down with variable renewable energy that can have no inertia at all, power-grid services need to change if we’re to maintain grid stability. “Renewables + storage” isn’t a luxury add-on; it’s the core design principle we must build around.

We can interpret storage in multiple ways, however. Short-term battery storage with its extremely fast response time is a great grid-balancing and stabilizing technology to deal with transient, short-term issues. Pumped hydro is slower to respond, typically requiring tens of seconds to ramp up, but it has an impressively large storage capacity, giving it the capability to assist with long-term (hours to days) stabilizing as a baseload supply. Other more exotic solutions like compressed-air energy storage could also play a part. Heat storage may also be useful, especially where we seek to store excess renewable energy over a daily or multi-day period.

We can also consider interconnectors as a kind of pseudo-storage system if we think about storage as a big bucket of power that we can fill or drain as needed. Large-scale interconnectivity can connect renewables from a high-production zone to one which is currently not producing, and vice versa when the situation demands. That expands the range of possible sources and spreads the variability of renewables across a larger, more diverse geography: the “wind is always blowing somewhere” philosophy. 

We also need to consider more active and modern automated control of our grid systems. We’ve designed them to protect themselves from gross anomalies such as frequency variations by the most aggressive of mechanisms. In most cases, if things go wrong, grid systems isolate themselves. We could envision future systems that are managed much more intelligently. AI offers the capability to actively control power generation to the grid and power flows, as well as storage capacity and technology centrally, making smart decisions about who to restrict, who to isolate, who to increase, and who to incentivize to do certain actions, based on second-by-second analysis of grid status. A smart system that runs hundreds of scenarios every second can make much better decisions than the semi-passive “all or nothing” system currently used. We need to start working to change those controllers now.

Pinning down the technical root cause doesn’t absolve us from the bigger task: upgrading generation and grid in lockstep. If we’re to have resilient power systems in the future, we must apply rigorous systems thinking, ensuring we modernize all aspects of our power systems in step with their components’ technical strengths and weaknesses.

For now, as we make this transition, I will be carrying a small amount of local currency wherever I go … a key travel tip painfully learned!