Blackout risk rises as heat wave stresses largest US electric grids

By Tim McLaughlin

Sept 2 (Reuters) – The risk of power outages is expected to escalate across a broad swath of the United States on Wednesday as intense heat will test ​the capacity of electricity supplies serving millions of homes ‌and businesses from the Midwest through the Mid-Atlantic.

The U.S. Department of Energy warned of the potential for heightened blackout risks in the PJM Interconnection, the largest U.S. electric grid, which serves 67 million people in a territory stretching from ‌Washington ​D.C. to Chicago.

Late on Tuesday night, DOE ⁠Secretary Chris Wright authorized PJM ⁠to direct backup generation resources to operate as a last resort before declaring a level 3 energy emergency alert, which can be one of the last steps before rotating blackouts are ​ordered.

The DOE said the move was part of a plan “to stabilize the Mid-Atlantic grid and mitigate the risk of blackouts.”

“Maintaining ⁠affordable, reliable, and secure power for hardworking ⁠American families and businesses during periods of hot ​weather is non-negotiable,” Wright said in a statement.

Temperatures in Chicago, St. Louis ​and Washington D.C. were expected to rise above 90 ‌degrees Fahrenheit (32 degrees Celsius) during peak electricity demand.

PJM’s “maximum generation emergency” alert in effect early on Wednesday directed generators on planned outages to report how quickly they could return units to service.

Meanwhile, the Midcontinent ⁠Independent System Operator (MISO), the regional grid operator for 15 U.S. states in the Midwest and the South, predicted peak demand on Wednesday would approach ⁠record territory at ‌about 121 gigawatts. MISO’s all-time high is 127.1 ⁠GW.

MISO warned of tight conditions and increased its ​normal ‌reserve requirement as a buffer against unexpected power ​plant outages and ⁠transmission line congestion.

In the Ozark region of rural Missouri, the Howell-Oregon Electric Cooperative advised customers to unplug unused chargers and appliances due to the continued extreme heat. Customers also were asked to consider raising their thermostats to reduce air conditioning use.

(Reporting by Tim McLaughlin; Editing ​by Jan Harvey)