Published September 4, 2026
By NZero
The latest heatwave across the US is putting electricity grids under significant pressure as temperatures rise and demand for power increases. On September 2, the US Department of Energy warned of heightened blackout risks across the PJM Interconnection, the largest US electric grid, which serves approximately 67 million people across an area stretching from Washington, D.C. to Chicago. At the same time, the Midcontinent Independent System Operator (MISO), which operates the grid across 15 states in the Midwest and South, forecast peak demand of approximately 121 gigawatts (GW), approaching its record high of 127.1 GW.
The situation illustrates a specific challenge for commercial and industrial energy users. Extreme heat can increase electricity consumption at the same time that the wider grid is operating with less available capacity. Cooling systems, refrigeration, industrial processes and other equipment can all contribute to higher facility-level demand. For businesses, understanding when and where that additional electricity is being consumed can help identify opportunities to manage peak demand and control operating costs during periods of intense heat.
Electricity demand typically increases during periods of extreme heat as homes and businesses rely more heavily on air conditioning. In the latest heatwave, temperatures in Chicago, St. Louis and Washington, D.C. were expected to exceed 90°F, or approximately 32°C, during periods of peak electricity demand.
The relationship between temperature and electricity consumption is particularly important because cooling demand can rise quickly. A building that operates normally during moderate weather may require significantly more electricity to maintain indoor temperatures when outdoor conditions become extreme. For a large commercial building, manufacturing site or warehouse, these increases can occur across multiple systems at the same time.
The impact can become more significant when many facilities experience the same conditions simultaneously. MISO expected demand to reach about 121 GW during the September 2 heatwave, only 6.1 GW below its historical peak of 127.1 GW. The operator warned of tight conditions and increased its normal reserve requirement to provide additional protection against unexpected power plant outages and transmission congestion.
PJM was also operating under a maximum generation emergency alert. Generators that were undergoing planned outages were instructed to report how quickly they could return units to service. The Department of Energy also authorised PJM to direct backup generation resources to operate as a last resort before a Level 3 energy emergency.
For businesses connected to these grids, the immediate concern may be reliability, but the energy-management question is more specific: how much electricity is a facility using during the hours when the grid is under the greatest pressure?
During a heatwave, cooling can become one of the largest drivers of electricity consumption in commercial and industrial facilities. HVAC systems may operate for longer periods, compressors may run more frequently and cooling equipment may work harder to maintain required temperatures.
The effect varies significantly by building and industry. An office building may experience its largest increase through air conditioning, while a manufacturing facility could see additional demand from process cooling, compressed air, ventilation and production equipment. Refrigerated warehouses, food facilities and data centres can have substantial cooling requirements even under normal conditions.
This makes it important to distinguish between total energy consumption and peak consumption. A facility may have relatively stable annual electricity use while experiencing sharp increases during several hours of particularly hot days.
For example, consider a facility that normally reaches 500 kilowatts (kW) of electricity demand in the afternoon. During an extreme heat event, its demand rises to 700 kW. The additional 200 kW could come from HVAC equipment, refrigeration, production systems or several loads operating simultaneously. Without sufficiently detailed energy data, identifying the source of the increase can be difficult.
Understanding this pattern gives facility managers a more actionable picture of energy performance. They can examine when consumption increases, compare usage across similar days, and determine whether higher demand is primarily associated with weather, operational changes or equipment performance.
This distinction matters when businesses are trying to manage electricity costs. Depending on the utility tariff and facility, demand charges can be based on the highest level of electricity consumption during a billing period. A short period of unusually high demand can therefore have a financial impact beyond the additional electricity consumed during those hours.
The response to extreme heat does not necessarily require facilities to reduce all electricity consumption. Instead, energy managers can focus on understanding which loads are essential, which can be optimised and which can potentially be shifted to another time.
Several approaches can be considered depending on the facility and its operating requirements:
The practical value of these measures depends on having sufficient visibility into facility-level consumption. A utility bill can show how much electricity was consumed over a billing period, but it generally does not provide the operational detail needed to determine exactly when and why demand increased.
Higher-frequency energy data can provide that additional context. Facility managers can examine consumption patterns across hours, days and sites, compare performance during similar weather conditions and identify equipment or facilities that behave differently from expected patterns.
The Missouri example in the Reuters report demonstrates the same principle at a different scale. The Howell-Oregon Electric Cooperative asked customers to unplug unused chargers and appliances and consider raising thermostat settings to reduce air-conditioning consumption during the extreme heat. For commercial facilities, the equivalent response can involve identifying controllable loads and determining which operational adjustments can be made before or during periods of high demand.
The current heatwave also highlights the value of preparing for peak conditions before they occur. Once a facility is already experiencing unusually high demand, energy managers have fewer options if they do not know which systems are driving consumption.
Historical energy data can help establish a baseline for normal operation. A facility can compare current electricity use against previous days, weeks or similar weather conditions to determine whether consumption is within an expected range. Across a portfolio, businesses can also compare facilities to identify locations with unusually high energy intensity or demand.
This type of analysis can be particularly useful for organisations operating multiple commercial or industrial sites. Two facilities may have similar floor areas or production volumes but significantly different electricity profiles. Investigating those differences can reveal opportunities for HVAC optimisation, equipment maintenance, operational changes or other efficiency measures.
Forecasting can also support proactive decision-making. If weather forecasts indicate several days of extreme temperatures, energy teams can review expected demand, identify potential peak periods and communicate operational measures to relevant facility teams in advance.
The goal is to give businesses a clearer understanding of their energy consumption before a high-demand event occurs. When facility teams know which systems are responsible for their largest loads and when those loads occur, they can make more informed decisions about where consumption can be reduced, shifted or optimised.
The September heatwave is placing major US electricity grids under significant pressure. PJM warned of elevated blackout risks across a region serving approximately 67 million people, while MISO forecast peak demand of about 121 GW, close to its 127.1 GW record. Grid operators responded by increasing reserves and preparing additional generation resources, while some electricity providers asked customers to reduce consumption.
For commercial and industrial facilities, these conditions highlight the importance of understanding electricity consumption at the time and equipment level. Extreme heat can drive cooling demand higher precisely when the wider grid is experiencing its greatest demand. Knowing which systems are creating peaks, how consumption changes with weather and which loads can be adjusted gives energy managers more options for responding.
As heat events continue to create periods of unusually high electricity demand, granular energy visibility can support practical decisions around cooling, equipment operation, load scheduling and peak demand management. For businesses, the ability to see where electricity is being used and how consumption changes during extreme conditions can be an important part of managing both energy costs and operational performance.
