Heat domes are high-pressure systems that act like lids trapping hot air over a region. According to NOAA’s National Weather Service, they can raise surface temperatures for days or even weeks.

During the summer of 2025, the United States set new records for power demand under a persistent dome. In July, demand in the United States topped 750 gigawatts on some record-breaking afternoons, with power providers scrambling to meet peak loads while infrastructure came under strain.

When energy systems are overstretched, the risk of brownouts or blackouts increases. In addition to the human health toll of extreme heat, an overtaxed grid poses significant business and economic risks by driving up costs, limiting output, and damaging critical infrastructure.

Heat domes and the climate connection

Chu Chup Hinh via Pexels

Heat domes are becoming stronger and lasting longer. According to entities such as the World Meteorological Organization, climate change makes certain extreme heat events at least twice as likely.

One study of the 2021 Pacific Northwest heat dome found it was 86% stronger than it would likely have been without human-driven climate change.

Heat increases energy demand

When heat domes roll in, the grid starts sweating right along with the rest of us. Air conditioners, commercial coolers, refrigerators, and fans all crank up, slurping electricity like marathon runners gulping water. During the 2025 heat wave, U.S. power demand set records from coast to coast.

Peak demand shifts depending on the time of day and where you are. In the Mid-Atlantic, transformer banks hum under the strain in late afternoons. In California, it’s the early evening AC surge that pushes the grid into “brace yourself” mode, sometimes triggering conservation alerts or rolling blackouts.

These spikes aren’t just abstract numbers — they come with a price tag. Utilities shell out extra generation costs and pay hefty premiums in capacity markets. For businesses, unmanaged peaks can mean skyrocketing energy bills, interrupted production lines, and even data centers throttling performance to keep the servers from cooking.

How heat impacts grid infrastructure

National lab studies funded by the U.S. Department of Energy consistently flag heat as a key stressor on electric grid infrastructure. Heat affects generation equipment and transmission lines, creating multiple points of vulnerability.

Impact on power plants

• Thermal plants — power plants that generate electricity by heating water into steam to drive turbines — lose efficiency during extreme heat
• Turbines and generators overheat, producing less power when the inlet air is hotter

Impact on solar panels

• Output declines with rising temperatures — each degree over 25°C (77°F) reduces efficiency
• Above 40°C (104°F), reductions intensify, especially with dust buildup or poor airflow

Impact on transmission lines and equipment

• Hot lines sag more, increasing the risk of faults
• Transformers and switchgear run hotter, risking breakdowns and accelerating wear
• Cooling systems may struggle to keep up, further stressing components

The overall effect is that these pressures increase the likelihood of operational failures, including brownouts or full blackouts.

Vulnerabilities in the U.S. power grid

Aging infrastructure

The U.S. grid is uneven in age and robustness. Many regions rely on decades-old wiring and transformers, with some components well past their intended lifespan. Others, like the Southwest and Midwest, are especially hard-hit during heat due to slower infrastructure upgrades and sprawling service areas that complicate maintenance.

Regional weak spots and interconnection issues

The North American Electric Reliability Corporation (NERC) oversees grid reliability standards and has repeatedly warned about regional weak spots and poor interconnection.

Weak tie lines (power lines that connect different regions of the grid to share electricity) in the Midwest limit the ability to move excess generation from other states during heat spikes. Sunbelt states sometimes lack capacity margins when demand surges, forcing utilities to issue conservation alerts.

A combination of heat, aging equipment, and limited investment

As NERC alerts show, outdated infrastructure can’t always adapt quickly to heat domes. This vulnerability is compounded by limited investment in grid hardening and modern control systems. That weakness creates risk for widespread outages when high demand, aging equipment, and extreme weather events collide, potentially leaving millions without power.

Cybersecurity vulnerabilities

Adding to these physical weaknesses, the grid’s increasing digitalization and reliance on connected control systems have made it a prime target for cyberattacks. According to NERC, the number of vulnerable points in the grid’s software and hardware grew by roughly 60 per day, reaching between 23,000 and 24,000 annually — significantly expanding the potential attack surface for state-sponsored or criminal actors.

What’s being done about heat domes?

Grid operators and regulators are using both short-term and long-term strategies to limit vulnerabilities and plan for the future.

• **Short-term: **Approaches include demand response programs that pay businesses to cut usage at peak hours. Public heat alerts urge consumers to shift usage to cooler times. Utilities also balance loads through real-time coordination and distributed energy resources such as rooftop solar and local batteries.
• **Long-term: **Federal funds are under review to finance grid modernization. Batteries and storage are being added to smooth peaks. Legislation such as the BIG WIRES Act aims to strengthen transmission across regions. Regional grid operators, including CAISO in California, PJM in the Mid-Atlantic, and MISO in the Midwest, have launched heat wave prep plans and capacity-upgrade roadmaps.

Economic effects of heat domes

Heat domes drive higher costs for utilities and consumers. As peak electricity prices jump, bills go up. Utilities may pass those expenses on through rate increases, sometimes prompting public backlash.

Manufacturing, agriculture, and healthcare industries also feel the squeeze. Hospitals and data centers need reliable cooling. Crop irrigation systems and automated greenhouses rely on grid power. Amid extreme heat, some facilities face rationing or must run expensive backup generators.

Energy price spikes often coincide with heat waves. Market data show wholesale prices doubling or tripling in some regions during peak events. That volatility can affect broader economic activities, especially in heat-sensitive sectors.

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