- A historic heatwave across the eastern US pushed the PJM Interconnection to forecast record peak demand of up to 166.3 GW, surpassing its previous record of 165.6 GW.
- To avert supply shortfalls, the US Department of Energy issued emergency orders under section 202(c), allowing PJM to direct backup generators and temporarily override environmental permits from June 30 to July 3.
- PJM simultaneously declared a Hot Weather Alert, a Maximum Generation Alert and a Load Management Alert, recalling maintenance outages and asking customers to reduce usage.
As the US East Coast baked under triple-digit temperatures this week, its largest power grid operator was forced to activate emergency powers.
The PJM Interconnection, which serves 65 million people across 13 states and the District of Columbia, warned that peak demand could soar to 166.3 gigawatts (GW) – beating the all-time record of 165.6 GW set in 2011. Forecasts from PJM showed that even modest forecasting errors could leave the grid short of capacity on 1–2 July.
Compounding the challenge, soaring humidity reduces the efficiency of thermal plants and causes transmission lines to sag, while heavy air-conditioning loads strain distribution systems.
On Tuesday, PJM filed an emergency request with the US Department of Energy, seeking authority to run generators that might otherwise be unavailable due to maintenance or environmental permits. Hours later, Energy Secretary Chris Wright issued two emergency orders allowing plants to run at higher output levels even if emissions exceed permitted limits, provided they document environmental impacts.
The grid operator also declared a hot weather alert, a maximum generation alert and a load management alert, signalling to utilities and large customers that they should prepare to curtail consumption. PJM recalled planned maintenance outages, asked some industrial users to reduce load and encouraged households to adjust thermostats and conserve energy.
The alerts triggered demand response programmes under which industrial facilities are paid to cut consumption at critical times. In extreme conditions, PJM can order rolling brownouts or temporarily disconnect data centres, though the operator said such measures were a last resort.
Load maxing
The emergency highlights several structural stresses facing US power systems. First, climate change is amplifying heatwaves, increasing both their frequency and intensity – heat waves raise electricity demand for cooling while simultaneously reducing generation efficiency and transmission capacity.
Second, the rapid growth of data centres and electric vehicles is adding new loads that are highly concentrated in certain regions. Analysts note that some US utilities have revised demand forecasts sharply upward, citing AI and cloud computing demands akin to adding a large industrial plant every few months.
Third, many coal and gas plants slated for retirement remain on the system because new renewables and storage are not being built quickly enough to replace them.
The DOE orders have drawn criticism from environmental groups, who argue that rolling back emissions limits – even temporarily – sets a dangerous precedent. But regulators emphasise that blackouts pose their own public health risks, especially during heatwaves.
PJM said it would ensure emissions are monitored and that plants operating under the order comply with all other regulatory requirements. The Federal Energy Regulatory Commission, which oversees bulk power markets, is expected to review the incident and consider whether PJM’s reserve margins and interconnection queue reforms are adequate.
Similarly, as Britain electrifies heating and transport, peak summer demand is set to rise. If extreme heat events like those seen last week become more common, the UK grid will face similar strains.
The event underscores the need for flexible generation, demand-side response, and investment in transmission upgrades and long-duration storage. It also illustrates the trade-offs regulators must make between environmental compliance and keeping the lights on in a warming world.
