The Iberian Blackout of 28 April 2025: what happened and what we learned
On the afternoon of 28 April 2025 the Iberian electricity system suffered its most severe outage in more than two decades. Analysis of causes and lessons regarding grid stability.
The Iberian Blackout of 28 April 2025: what happened and what we learned
On the afternoon of 28 April 2025 the Iberian electricity system suffered its most severe outage in more than two decades. Just after 12:30 p.m., renewables were supplying 78 % of demand, with solar alone providing almost 60 % and conventional technologies (gas and nuclear) making up only 15 %. Minutes later two consecutive generation losses occurred in southwestern Spain, most likely at large solar plants. The losses coincided with limited conventional capacity and reduced support from neighbouring systems; the resulting instability led to a disconnection from the French grid.
Within five seconds Spain lost about 15 GW of capacity—around 60 % of national demand. Automatic protection systems disconnected additional generators and nuclear reactors were shut down for safety. An initial fact‑finding report notes that between 12:32 and 12:33 p.m. the Iberian grid lost 2.5 GW of renewable and thermal generation, causing voltage to surge from 400 kV to 435 kV and frequency to drop from 50 Hz to 47 Hz. The Iberian system desynchronised from the rest of Europe and interconnections with France and Morocco tripped offline.
The delay in activating frequency‑control reserves appears to have worsened the event. Spain’s transmission operator REE did not dispatch frequency containment or restoration reserves until after midnight on 29 April. Analysts argue that dispatching 1.5–2 GW of reserve generation within 30 seconds of the first loss could have prevented the cascade. Nevertheless, restoration began around 5 p.m. thanks to black‑start capable plants. Cross‑border links played a critical role: Morocco supplied up to 900 MW and France up to 2 GW via their interconnectors. By 6:00 a.m. on 29 April the system had restored 99 % of demand.
Some critics blamed renewable generation for the blackout, but official assessments dismiss that theory: weather conditions and renewable output were typical for the time and similar to previous days. Energy minister Sara Aagesen told lawmakers that the initial failures were traced to substations in Granada, Badajoz and Seville, causing 2.2 GW of lost generation, but emphasised that investigations continue. She ruled out a cyberattack or a supply‑demand imbalance and said the fault may have been linked to excess voltage in the days before. The European Network of Transmission System Operators for Electricity (ENTSO‑E) set up an expert panel on 12 May to investigate the incident. Its factual report, released in October 2025, confirms there was no cyberattack and attributes the successful restoration to coordinated work by REE, Portugal’s REN and France’s RTE.
Lessons for high‑renewable systems
The blackout exposed the vulnerability of electricity systems with low inertia. Most renewables use inverters that follow the existing grid frequency and do not provide electrical inertia; without enough synchronous generators (thermal, hydro or nuclear) the grid cannot absorb disturbances. Experts recommend:
- Investing in grid‑forming inverters that mimic the behaviour of conventional generators and contribute to frequency stability.
- Developing storage and pumped‑hydro plants: batteries and pumped storage can inject power rapidly during faults, although they also require advanced inverters.
- Reinforcing interconnections between Spain and France and enhancing grid flexibility.
- Improving frequency reserves and rapid‑response mechanisms, ensuring they activate immediately after generation losses.
Although the event was dramatic, it does not undermine the role of renewables. Spain continues to enjoy competitive prices thanks to wind and solar, and decarbonisation remains a strategic goal. Instead, the incident shows that the energy transition demands modern, flexible and resilient grids capable of integrating high shares of clean energy without compromising security of supply.
Maximize Your Savings
Understanding the market is the first step. The second is making sure you are on the best rate. Compare electricity providers in Spain and switch in minutes.