Excess mortality attributable to the 2025 Iberian Peninsula blackout

On 28 April 2025, a widespread power outage affected mainland Portugal and Spain for around ten hours, causing major disruptions and eight reported deaths. Health impacts of blackouts range from direct effects, such as medical equipment failure, to indirect effects such as disrupted healthcare. Here we show that the 2025 Iberian blackout is associated with increased mortality in Spain, but not in Portugal. We find little evidence of excess mortality on the day of the event itself. In Spain, however, mortality rises over the next two days (+167 deaths; 95% credible interval: +28 to +300; +2.4% relative increase), particularly among women aged 85+. We also observe regional differences, but their drivers remain uncertain and may include variation in outage severity, underlying vulnerabilities, or local health-system and infrastructure conditions. These findings highlight the underestimated health burden of blackouts and the need for improved preparedness in a changing climate.