While Spain and Portugal are slowly recovering from the electricity blackout that put both countries to a standstill, experts have been pointing out that renewable energy might be the main cause of the problem.
The origin of the outage was a sudden loss of 15 gigawatts of energy, the equivalent of 60 per cent of the area’s energy demand at that time.
While government officials said they were still searching for the cause, calling the blackout “hard to explain” and “very strange”, they did rule out hacking or cyberattacks.
Spain already had some organisations warning of exactly the scenario that played out. One consumer group called No Al Apagón (No to the Blackout) had been saying energy Spain’s policies were highly risky, threatening supply.
In its manifesto, published in September 2023, No to the Blackout warned that moving away from supply and demand and favouring market intervention could prove disastrous. It emphasised that was particularly the concern when the necessary investments had not been made in the grid or in the storage capacity for the switch to renewables and electrification to take place efficiently.
“It will generate supply cuts and blackouts, it will end that security we have had for more than 25 years,” it claimed.
What happened in Spain yesterday? On April 28, 2025, Spain witnessed a major energy event: a nationwide blackout.
What was the cause? A massive overload of the electrical grid due to a huge spike in solar production.
What happened?
At around 11:00 AM, Spain’s solar power… pic.twitter.com/UTcSrJRc1T
— Cata Paul (@CataPaul2) April 29, 2025
Alexander Stahel, a Swiss value investor in energy stocks, highlighted what he said was the connection between the outage and renewable energy and noted the relative fragility of the grid due to high renewable energy usage.
At the time of the latest blackout, Spain and Portugal were operating with a high share of renewables — 66 per cent of the combined grid’s power came from solar (55 per cent) and wind (11 per cent).
Renewables including solar and wind contributed little to no inertia to the grid. Inertia is crucial for stabilising the grid’s frequency during disturbances.
Stahel said traditional plants with synchronous generators, such as nuclear plants, provided significant inertia due to their heavy, spinning turbines. For example, a 1,500MW nuclear plant contributes 5,000 to 7,000 MW-seconds of inertia, he said, while a 4MW wind turbine provides only 2MW to 5MW-seconds – more than 1,000 times less.
Solar panels, which produced direct current (DC), must be converted to alternating current (AC) for the grid and they contribute essentially zero inertia, he added.
Wind turbines, while they have spinning blades, were often asynchronous, or used converters, limiting their inertia contribution unless equipped with synthetic inertia mechanisms, Stahel pointed out.
Due to hot weather in France and Italy, there had been high demand for cheap Iberian solar power, leading to heavily loaded transmission lines from Spain to France. These lines were operating near their stability limits, leaving little capacity to handle sudden shocks, Stahel stressed.
A disturbance on a major 400kV transmission line between Spain and France appeared to have caused two circuits to trip simultaneously, experts suggested.
Spain and Portugal experienced a major power outage that disrupted public transport, caused heavy traffic congestion, and delayed numerous flights. Utility operators worked urgently to restore the electricity supply. https://t.co/C5p5HDWff8
— Brussels Signal (@brusselssignal) April 28, 2025
The low inertia exacerbated the issue: Frequency oscillations between Iberia and continental Europe became unstable, with divergences exceeding 200mHz. This led to the Iberian Peninsula electrically “islanding” from the European grid, Stahel said.
Solar inverters disconnected rapidly due to the fast frequency changes (high rate-of-change-of-frequency, or RoCoF) and further generators tripped, causing a collapse in parts of Spain, he added.
Stahel stressed that was a preliminary analysis, pending a full report from the European Network of Transmission System Operators (ENTSO-E).
A similar argument was made by US journalist and environmental activist Michael Schellenberg.
Excess solar power led to too little inertia, causing the system to collapse, Schellenberg said on X on April 28.
Renewables such as solar did not provide the rotating mass needed to stabilise the grid, making it susceptible to blackouts during disturbances, he added.
Belgian Professor Damien Ernst, a specialised in energy, similarly highlighted the issues with inertia and the balance between power production and consumption that he believed most likely led to the collapse of the grid.
“Lack of inertia in the Spanish power system due to renewables clearly played a key role. But it is much more than this. We may be facing fundamental design flaws, which is scary because it may make these events more and more frequent,” he warned on April 29 on X.
Energy economist Björn Peters told German news outlet Apollo News on April 28 that “because in Spain as in Germany high proportions of PV systems cannot be controlled, fewer and fewer power plants are available to react to instabilities”.
“The system is therefore slowly becoming more and more unpredictable. Even small disruptions can then lead to uncontrollable failures of large systems,” he said.
The hundred percent rebuildable dream has started pic.twitter.com/hSccbYrcHm
— Pembridge Cap (@pembridge_cap) April 28, 2025
On April 24, Bloomberg columnist Javier Blas had warned in a comment piece: “Electrifying everything comes with plenty of risks of its own.”
“Unfortunately, ‘green’ activists, who hardly see any problem with electrifying everything, believe any concerns represent little more than attempts to delay a needed transition away from fossil fuels,” Blas said.
“Systemic challenges will emerge from balancing increasingly renewable-dominated grids during extended low-generation periods,” he added, quoting the Paris-based International Energy Agency (IEA).
Blas highlighted that supply and demand must match all the time, but that, unlike fossil fuels or nuclear, renewable was extremely vulnerable on that front. “A pylon that goes down can trigger a regional blackout; a cyberattack can disconnect large swatches of the network,” he said.
Two weeks earlier, Bloomberg had already pointed out the danger of Spain going all-in on renewables and being only second to Germany in terms of renewable capacity in Europe.
In mid-April, Spain boasted it generated 100 per cent of its electricity needs from renewable energies in one moment for the first time.
In 2024, this figure was 56 per cent, according to Spanish grid operator Red Eléctrica.
Brutal, just brutal pic.twitter.com/oeGxbXnobS
— Velina Tchakarova (@vtchakarova) April 29, 2025
Following the latest blackout, Spanish Prime Minister Pedro Sánchez said the Government would investigate what had happened and demanded private operators take measures so that it was “never repeated”.
He denied the outage was due to a lack of nuclear plants. “If we had had greater nuclear dependence, the recovery would not have been as fast as the one we are experiencing,” claimed Sánchez, who added that he would request an independent report from Brussels.
Opponents of the PM said Spain had been left looking like a third-world country, akin to Cuba or Venezuela, where electricity outages also occur.
In 2022 during an appearance in the Senate, Sánchez had stressed that there would be no blackouts in Spain, accusing “the Right and the ultra-right” of suggesting that they could happen in light of the war in Ukraine. Clips of this went viral on April 28.
Unlike any other European countries, the progressive Spanish Government has continued to close down nuclear power plants, aiming to be nuclear-free by 2035.
Southern Europe was hit by a major electricity outage affecting millions of people in the Iberian Peninsula and beyond, paralysing infrastructure, communication and transportation. https://t.co/2oYvCGK9CN
— Brussels Signal (@brusselssignal) April 28, 2025
