Spain & Portugal Blackout: What Really Happened?
- August 19, 2025
A sudden collapse of the Iberian power grid at approximately 12:30 p.m. local time on April 28, 2025, plunged Spain and Portugal into darkness, with the disruption also affecting southern France. While island territories were spared due to separate systems, the event ranked among the most severe blackouts in Europe’s modern energy history.
Power started coming back online around 5 p.m. and was steadily restored throughout the night, with 99% of demand met by 6 a.m. the following morning, a recovery hailed as swift and effective. Still, the outage had already taken a toll, leaving thousands stranded in trains, elevators, and other electricity-dependent systems, and resulting in at least seven casualties.
Investigators pointed to severe voltage fluctuations as the spark that brought down Spain and Portugal’s grid. Both the government and transmission operator Red Eléctrica de España (REE) agreed that an overvoltage set off a chain reaction of shutdowns, overwhelming safeguards, and crippling essential services. While their reports differ on why the surge could not be contained, they converge on one key point: overvoltage was the trigger.
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The blame game
According to BloombergNEF’s Eva Gonzalez Isla, the Spanish government pinned blame on REE for failing to secure adequate voltage control, while also faulting contracted power plants that not only failed to stabilize the grid but worsened the crisis. REE, however, rejected this, insisting it delivered sufficient support and arguing the fault lay with the plants that failed to perform.
Isla explained that overvoltage occurs when electricity surges beyond safe operating levels, forcing automatic protections across the grid to step in. These safeguards are designed to disconnect power plants, factories, or even households once voltage strays outside a set range.
When one plant trips, the imbalance can trigger neighboring facilities to shut down too, sending voltage even higher and unleashing a domino effect that can spiral into a blackout. While this prevents catastrophic damage to equipment, it also disconnects large sections of the grid — and doesn’t guarantee all machinery will be spared.
“Even if the protections act and disconnect some of your equipment, that doesn’t mean that all your equipment is going to be undamaged,” said Isla. “There’s electrical industrial equipment. For example, aluminum smelters–if they don’t have constant power at all times, they’re very hard to run. So there’s, you know, not all machinery can be saved, even in the event of overvoltage.”
CaixaBank estimated that Spain’s blackout shaved nearly €400 million off the economy. Using payment data, the bank found household spending collapsed by a third during the outage and, though activity rebounded in the days after, it still lagged about 15% below normal levels, leaving a measurable dent in GDP.
Are renewables the culprit?
Spain has become a renewable powerhouse, with wind and solar generating about 43% of its electricity, well above the global average, according to Ember. In Spain and Portugal, gas and nuclear together account for only around 15% of supply, a relatively small share that reflects the region’s reliance on favorable weather conditions. Spain is set to end coal-fired power by 2025, having already closed its largest plant last year.
REE reported that two likely solar plant failures in the southwest triggered instability that severed Spain’s grid link with France. At the time, Spain had been exporting heavily, with flows to France near the grid’s export limit until late morning. Those exports collapsed at 12:35 p.m., dropping abruptly from 868 megawatts (MW) to zero.
According to the Baker Institute for Public Policy, the blackout highlighted the vulnerability of grids that rely heavily on renewables, a risk long recognized by energy experts. The main challenge is the shortage of ancillary services, particularly frequency control and inertia, which conventional plants such as nuclear, thermal, and hydro normally provide through their rotating machinery to stabilize the grid during sudden swings.
The Guardian also pointed out that managing a grid dominated by renewables poses greater challenges than one built around fossil fuels. Traditional coal, gas, and nuclear plants use spinning turbines that provide inertia to keep frequency stable near 50 hertz (Hz). Wind and solar lack this buffer, making it harder to absorb sudden shocks, with sharp drops risking automatic shutdowns and potential system collapse.
Isla confirmed that renewables don’t have inertia. “Inertia is basically at which speed the frequency will change depending on the supply and demand balance,” she said. “So if you have a system with more inertia, it means that if one generation drops to have more time, it buys you time to solve this frequency and balance.”
Unlike traditional plants, solar and wind farms rely on grid-following inverters that match the frequency and voltage already in place rather than setting them. This makes them dependent on a stable system and unable to independently stabilize the grid when disruptions occur.
With conventional plants supplying little power on April 28 and solar dominating the mix, the Iberian grid had scant inertia to cushion sudden shocks. “This meant that the Iberian system lacked the inertia needed to absorb the initial generation-loss shocks,” wrote Raul Bajo Buenestado of the Baker Institute. “Automatic protection mechanisms were triggered, including the disconnection of transmission lines and generating units, ultimately resulting in cascading power outages.
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Moving forward
Interviewed by The Guardian, Charmalee Jayamaha, senior manager at Energy Systems Catapult, noted that the transition to renewables was reshaping the electricity grid and creating new resilience challenges. “Resilience is no longer just about having enough spare megawatts you can simply switch on,” she stated. “But about the right mix of technologies and system capabilities to operate a grid with a lot more renewables.”
Meanwhile, Isla shared that REE had long urged regulators to modernize rules on voltage control, arguing that reliance on conventional left gaps as renewables grew. Those gaps were exposed during the recent blackout, when limited interconnection between France and Spain triggered frequency oscillations that conventional controls only worsened. She also noted that Spain, like other relatively isolated grids, must also embrace advanced stabilizing technologies like synchronous condensers—spinning machines equipped with modern power electronics that boost inertia and help balance voltage.
“The government announced…they’re going to invest €750 million on the grids, and part of that is to buy eight synchronous condensers for mainland Spain, and that would save the system something like €200 million a year,” she explained.
Another stabilizing technology is the grid-forming inverter, which lets renewables set grid voltage and frequency, echoing the role once played by fossil-fuel generators. However, Buenestado mentioned that while grid-forming inverters are emerging as a key tool, they remain largely untested at scale. Proven in smaller systems like those in Australia and Hawaii, their deployment in complex, interconnected grids poses challenges, particularly around coordinating multiple devices without creating conflicting frequency signals.
“Current research is exploring new approaches that involve coordinating multiple grid-forming inverters to work together to maintain grid stability,” he wrote.
Sources:
https://open.spotify.com/episode/1wHEArYpgz0IoSsCNYvOOm?si=67287f85e180415f
https://www.brusselstimes.com/1566479/blackout-cost-spain-e400-million
https://www.reuters.com/world/europe/what-could-be-behind-iberian-power-outage-2025-04-29
https://www.theguardian.com/business/2025/may/02/blackouts-energy-outage-risks-europe-worldwide-spain-portugal-france
