Audio recordings reveal warning signs months before 2025 blackout

Audio recordings between Spain's national grid operator Red Eléctrica (REE) and various energy companies reveal that network instability issues had already surfaced months before the general blackout in April 2025.

The Catalan News Agency (ACN) has had access to a series of communications showing that technicians detected irregularities in the system as early as January 2025. 

In one exchange between utility company Endesa Barcelona and the REE control center on January 31, operators reported a "sudden voltage drop" and asked for clarification.

REE acknowledged the incident, attributing it to photovoltaic producers releasing "a huge amount" of megawatts into the grid. 

"It was a very strong oscillation," control center staff said, describing the event as "very large" and noting that "all distributors have seen it, as is normal."

Further recordings from April 7, just weeks before the blackout, show that system inertia problems had already happened, raising concerns among REE technicians amid a drop in nuclear generation, which typically helps stabilize the network.

In an exchange between Seville and the REE control center, operators warned they would have to cope with ongoing inertia issues and cautioned this could lead to a "tipping point."

An EU report downplayed the role of renewable energy sources in causing the incident.