A ‘sudden and severe’ imbalance in the Iberian Peninsula’s power grid has been identified as the cause of the ‘historic’ blackout that affected Spain, Portugal and parts of France on Monday.
The sudden imbalance was caused by a rapid drop in the use of solar power in Spain, which fell from 18 to eight gigawatts in the space of just five minutes, reports Reuters.
This was behind the ‘strong oscillation in power flow’, which saw electricity generation suddenly plummet.
As a result, the wider European network disconnected the Iberian grid in a bid to prevent further instability.
Spanish Prime Minister Pedro Sanchez said the country lost 60% of national electricity supply in just five seconds.
The country then had to reconnect each power plant to the grid, one by one, in a process that took almost 24 hours. Spain also increased power imports from France and Morocco to help.
Spain’s national utility company Red Eléctrica earlier ruled out a cyberattack, human error, or some unusual meteorological or atmospheric phenomenon as being the cause.
It pointed to two episodes of ‘generation disconnection,’ most likely involving solar power generation.
In a press conference on Tuesday afternoon, PM Sanchez said: ‘I want to acknowledge and thank the extraordinary work of our public servants from all administrations. They more than fulfilled their duty.
‘And to achieve this, they counted on the complicity of a great society that once again demonstrated maturity, responsibility, and civic spirit.’
He vowed to get ‘to the heart’ of the cause of the blackout and said ‘this can never happen again’.
Below are other key findings from the past few hours.
Lower ‘inertia’, higher risk
At the heart of Spain’s blackout appears to be a hidden vulnerability: inertia – or rather, the lack of it.
Traditional power plants contain giant spinning turbines that produce a kind of energy buffer. This ‘inertia’ buys operators precious seconds to respond when the power grid lurches due to sudden spikes or drops in demand.
But in a system increasingly powered by the sun and wind, inertia is fading fast. Unlike gas or coal, solar panels and wind turbines are hooked in through electronic inverters. They don’t spin nor store that stabilising energy.
So when solar generation collapsed in minutes on April 28, the Iberian grid, light on inertia and heavy on renewables, had nothing to catch its fall.
Spain relies on wind and solar for 43% of its energy, well above the global average.
At the time of the blackout, solar photovoltaic (PV) accounted for 59% of the country’s electricity.
Theories shot down
As power vanished across Spain and Portugal, conspiracy theories lit up almost as fast.
Spain’s National Cybersecurity Institute (CNI) quickly rubbished cyberattack fears, saying there was ‘no evidence’ to support the claims.
It came after Andalucia president Juan Manuel Moreno had said on Monday that the outage ‘was due to a cyberattack’, citing information from the region’s cybersecurity centre.
The CNI had detected ‘significant unusual activity originating from North Africa’ in the days before the blackout, according to sources from the security agency speaking to Servimedia.
However, government minister Teresa Ribera later said that ‘for the moment there are no signs of sabotage’.
Prime minister Sanchez also made no reference to an attack and urged people to avoid speculation.
It came after reports that rare atmospheric conditions, or ‘induced atmospheric vibrations’, tampered with the high-voltage lines. While technically possible, experts agreed that it was also highly unlikely.
Lessons to be learned
As the investigation continues, many are seeing the events in Spain as a potential warning.
As countries race to ditch fossil fuels, they’re building grids that run cleaner, but not necessarily stronger.
Experts now warn of a gap between ambition and infrastructure. Without backup systems – batteries, synthetic inertia, or rapid-response stabilisers – future blackouts may come not in decades, but in years.
The power grids of the future must be not only green, but resilient.
