Amid Uncertainty, These Are The Facts: Understanding The Iberian Outage

Amid Uncertainty, These Are The Facts: Understanding The Iberian Outage

The unexpected power outage across Spain and Portugal on Monday 28^th April raised more questions than answers. With the root cause still under investigation, speculation has filled the gap left by official reports. However, even in the absence of full clarity, some technical truths remain. Understanding what could – and could not – have caused the event is crucial to shaping a more resilient and better-informed energy transition.

Here are some key facts that help frame the situation and provide context on how the grid functions, where vulnerabilities lie and what needs to be strengthened moving forward:

• The problem was not a generation shortfall.
  The Iberian outage was not caused by a lack of electricity supply or insufficient generation capacity. In fact, available generation was sufficient to meet demand at the time. The issue was a sudden imbalance and instability in system frequency, likely triggered by a technical fault or grid disturbance, though the exact cause is still under investigation. When frequency deviations exceed safe operational thresholds, automatic protection systems are activated to isolate and shut down parts of the grid to prevent further damage. In this case, the imbalance is suspected to have originated in two points in the south west followed by a disconnection from the French network, and the automatic response to the cascading effect was so widespread that it led to outages across the entire peninsula.
  
  
• More nuclear capacity wouldn’t have prevented the outage.
  While nuclear energy is important for providing stable baseload generation, it’s not suited for real-time grid-balancing. Nuclear plants are not fast-start resources: they can’t ramp up quickly to support recovery after a system disturbance. In fact, during major grid events, nuclear units often trip offline to protect themselves and can take hours – or longer – to restart. They also don’t typically participate in primary or secondary frequency regulation. Instead, flexible assets like hydro, gas peakers and battery storage are far more effective in stabilizing the grid during sudden disruptions.
  
  
• Renewable generation is not to blame – but it does need flexible support.
  Wind and solar are variable and typically non-dispatchable. Their reliance on inverter technology means they lack the rotating inertia and that their output can’t be adjusted on demand. While renewables aren’t the direct cause of frequency disturbances, relying solely on them without adequate balancing assets like batteries and rotating shock absorbers – like pumped hydro, or combined-cycle gas turbines – can increase system vulnerability. Spain’s recent milestone of reaching 100% renewable mix on April 16, 2025, shows what's possible to achieve, but grid resilience requires the capacity to respond swiftly to rapid frequency changes – even those as extraordinary and unprecedented as Monday’s incident.
  
  
• Decentralization matters.
  Although renewables do not inherently provide operational inertia or ramping capabilities, their decentralized nature proved beneficial during the restoration phase. The distributed layout of solar and wind farms enabled a modular and rapid re-energization of the grid. In fact, during the first two hours after the outage, over 70% of the restored power came from renewable sources. This underlines the importance of a distributed energy system in improving resilience and restoration capability.
  
  
• Reinforcing cyber security is fundamental.
  There has been no official confirmation regarding the exact source of the frequency disturbance. While EU authorities and Spanish system operator Red Electrica have stated that there is currently no evidence of a cyber attack, the Spanish Government has not ruled out this possibility. Regardless of the cause in this case, the increasingly digital and interconnected nature of electricity systems makes them more vulnerable to cyber threats. Strengthening cyber security protocols and real-time monitoring systems is essential to safeguard critical infrastructure.
  
  
• Demand-side response is an underused flexibility resource.
  Grid flexibility shouldn’t rely solely on generation. Demand-side response (DSR) – where large consumers temporarily reduce or shift electricity use – can play a vital role in stabilizing frequency and preventing widespread outages. Despite its potential, DSR remains underutilized in Spain and Portugal. At critical moments, like Monday’s event, enabling demand to actively support the grid could help reduce the scale of disruption, ease the burden on generators and improve the overall resilience of the system.
  
  
• Advanced grid management systems are essential, but still maturing.
  Outage management systems, digital grid technologies and real-time monitoring tools are crucial for improving grid reliability and for accurately detecting, reporting and analysing disturbances. However, this severe outage highlights that these systems are not yet fully implemented or sufficiently coordinated across all levels of the power system. With the root cause of the outage still unconfirmed, it’s clear that more advanced and integrated grid management capabilities are needed – not only to improve response times but also to ensure clear and transparent communication and prevent future incidents.