Power Grid for 67 Million at Risk as Deep Freeze Follows Storm

A deep freeze is gripping the US as the worst storm so far this season winds down, leaving the country’s biggest electric grid in emergency status and bracing for record wintertime demand.

PJM Interconnection LLC, which serves 67 million people from New Jersey to Chicago, issued a grid emergency for Tuesday and warned demand will exceed 147 gigawatts, an all-time high for winter. With another burst of frigid air expected Friday, electricity demand could remain above 140 gigawatts — roughly the output of 140 large nuclear reactors — through the end of the month.

Freezing temperatures now cover vast ...