On March 13, 1989, a geomagnetic storm spawned by a solar outburst struck Earth, triggering instabilities in the electric-power grid that serves much of eastern Canada and the U.S. The storm led to blackouts for more than 6 million customers and caused tens of millions of dollars in damages and economic losses. More than 25 years later, the possibility of another such catastrophe still looms, and the day-to-day effects of space weather on electrical systems remain difficult to quantify. Now, a new study correlating electrical insurance claims with geomagnetic data suggests that even moderate space weather may play a significant role in destabilizing the power grid.