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, like fires and medical equipment failure, to indirect effects such as disrupted healthcare. We present the first systematic assessment of mortality linked to this event, disentangling impacts by age, sex, and region. Using advanced Bayesian models that accounted for temperature, holidays, and spatiotemporal trends, we estimated expected deaths during the blackout week. Comparing observed to expected mortality, we found limited excess deaths on the blackout day. In Spain, mortality rose over the next two days (+167 deaths; 95% Credible Intervals: +28 to +300), particularly among women aged 85+. No clear excess was found in Portugal. Regional differences suggest varying healthcare resilience. Findings highlight the underestimated health burden of blackouts and the need for improved preparedness during the climate crisis.