The blackout, which lasted for over 36 hours, resulted in a significant decline in mobile network performance, as backup power systems failed and traffic loads overwhelmed already stressed mobile grids. Industry experts are warning that the event highlights the critical need for enhanced resilience and continuity of service, particularly as the telecoms industry transitions to renewable energy sources.
According to analysis from Speedtest Intelligence by Ookla and Downdetector, mobile network performance in both countries deteriorated sharply after the power failure, with the impact peaking in the early afternoon.
The outage triggered a cascade of failures across mobile networks, affecting nearly all operators. By 12:00 PM CET on April 28, the share of Spanish users experiencing a stable connection, defined as minimum 5mbps download and 1mbps upload speeds, had plummeted to 50%.
By 3pm, this figure had dropped even further to just 40%. In Portugal, the situation was even worse, with the share of users able to maintain a consistent connection dipping below 40% by 2 PM.
Cascading failures and performance drops
The collapse of mobile services was closely tied to the power grid outage, with mobile performance tracking grid restoration patterns. In areas where power was restored quickly, such as parts of Madrid and central Spain, mobile performance recovered faster.
However, in regions such as the Valencian Community, Galicia, and parts of Portugal’s coastal corridor, service remained disrupted for hours. In Spain, download speeds in some areas fell by as much as 85%, while in Portugal, speeds in regions like Porto and Vila Real dropped by 90%.
The outage exposed significant vulnerabilities in the telecommunications infrastructure, particularly in terms of backup power capacity. In regions where mobile sites had access to battery backups or generators, service remained somewhat more stable, but in many areas, network performance was severely hampered due to increased load from migrating users and the absence of fixed broadband alternatives.
The scale of the outage was such that users in some areas were unable to access any mobile network services, with many experiencing failed Speedtest sessions as they attempted to diagnose the connectivity issues.
Luke Kehoe, an industry analyst at Ookla, pointed out that this event underscores the importance of ensuring that telecoms infrastructure is designed to withstand such large-scale disruptions.
"The blackout has highlighted the vulnerabilities in mobile network infrastructure, especially when the grid goes down. While renewable energy is an essential part of Europe’s future, we need to ensure that the telecoms industry can maintain reliable service, even during power outages," he said.
Economic and social impact
The economic consequences of the blackout are significant. The Spanish economy alone faces an estimated €1.6 billion in losses, with major impacts on manufacturing, logistics, and retail sectors. The loss of mobile services, particularly during peak business hours, exacerbated the situation.
Hospitals had to switch to backup generators, disrupting surgeries and medical treatments, while airports and train stations were forced to halt services, leaving thousands of passengers stranded.
The blackout also highlighted the growing dependence on mobile networks for day-to-day activities. In the absence of a stable fixed broadband infrastructure, many people relied on mobile networks for internet access. The collapse of mobile services, particularly in rural and coastal areas, left large sections of the population without access to communication and information for prolonged periods.
Lessons from the outage
While mobile networks in Spain and Portugal struggled, certain operators managed to provide slightly better performance than others. In Spain, Movistar outperformed its competitors, maintaining higher download speeds and lower latency.
In Portugal, Vodafone led the pack, surpassing NOS and MEO in terms of network performance. However, the overall scale of the disruption, which impacted all operators, demonstrated the need for industry-wide improvements in infrastructure resilience.
"The event serves as a reminder of the importance of network resilience," Kehoe added. "It’s not just about having backup power, but ensuring that mobile networks are capable of managing sudden surges in demand, especially when grid failures occur."
Looking to the future, there are lessons to be learned from other countries that have successfully integrated greater resilience into their telecoms infrastructure. For example, Nordic countries such as Norway and Finland have introduced regulations mandating minimum hours of mobile service continuity during power outages. In Australia, a government-backed programme retrofitted hundreds of mobile sites with backup power capabilities to prevent similar disruptions.
Call for policy change
In the wake of this event, there have been calls for greater investment in telecoms infrastructure and policy reforms to ensure the continued availability of mobile services during power outages. The European Union is expected to launch an independent inquiry into the incident, with many experts suggesting that telecom regulators across Europe must act swiftly to strengthen mobile network resilience.
As Spain and Portugal continue to recover from this unprecedented outage, the incident is likely to prompt further discussions around energy policy, the integration of renewable energy into national grids, and the critical role of telecoms in modern society.
Kehoe concluded: "The best time to strengthen mobile networks is before the lights go out. As renewable energy continues to grow in importance, we must ensure that the telecoms industry is prepared for the challenges posed by this transition."
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