The wholesale blackout which rendered most of the Iberian Peninsula, including its data centers, without power in April was the result of a series of smaller interacting problems, the Spanish government has said.

A government investigation found that efforts by Red Eléctrica de España, Spain’s grid operator, to address a small instability in the system actually led to more severe issues, causing a self-reinforcing cascade where high voltages caused power plants to drop off the grid.

Sara Aagesen, deputy prime minister and minister for the ecological transition of Spain, said the report, showed that Red Eléctrica had miscalculated the power capacity needs for the day, leading to the system to “not have enough dynamic voltage capacity.”

She went on to say that the regulator failed to switch on another thermal generation plant, deeming that it was not necessary, compounding the issue. According to the report, the grid operator only had ten power plants to handle voltage regulation on the day of the blackout, the lowest it had committed in all of 2025. Several of the plants subsequently failed to respond, leading to further problems.

In addition, it was found that some grid hardware disconnected prior to reaching the mandated threshold – at which grid hardware needs to disconnect to protect the equipment – which led to fluctuations in voltages and an imbalance between northern and southern Spain. This ultimately led the system to shut down, causing mass power outages across both Spain and Portugal.

Aagesen also pointed the finger at private generation firms in failing to regulate the grid’s voltage prior to the blackout, stating: “Generation firms which were supposed to control voltage and which, in addition, were paid to do just that did not absorb all the voltage they were supposed to when tension was high.”

Red Eléctrica has subsequently disputed the report’s findings, with its operations chief Concha Sanchez telling a news briefing that its own investigation had found anomalies in the disconnection of power plants. Sanchez went on to say that the grid operator would release a full report on the causes of the outages.

The outage wreaked havoc on the region’s Internet and telecommunications services. In Spain, Internet traffic dropped 60 percent compared to the previous week as the power grid failed, falling to approximately 80 percent below the previous week within the next five hours.

Wireless operators, with a large footprint of cell towers across the region, turned to backup generation to keep their networks online.

The data center sector was able to avoid the worst impacts of the outage by turning to its diesel backup generators.

Equinix noted to DCD Spain: “Equinix data centers in Spain and Portugal are fully operational and have been throughout the blackout. After the interruption of the electricity supply, emergency systems were activated to ensure service without interruption. With the restoration of supply, all our data centers in both Spain and Portugal operate normally.”