Blackout risk rises as heatwave stresses largest US electric grids

US energy department warns of potential for outages in PJM Interconnection, serving 67 million from DC to Chicago

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

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

The energy department 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 DC were expected to rise above 90F (32C) 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 US 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.