A solar storm on the scale of the 1859 Carrington Event would knock out large sections of the U.S. power grid for weeks or months, producing economic losses estimated between $0.6 trillion and $2.6 trillion. That range, drawn from analyses by the National Research Council in 2008 and Lloyd’s of London in 2013, reflects damage to high-voltage transformers, satellite communications, and supply chains that depend on continuous electricity. The sun is now climbing toward its next activity peak, and the bulk of the grid hardware that would absorb the blow has not been replaced or shielded since those estimates were published.
Why the Carrington threat is sharper in 2025 than in 1989
The clearest modern precedent for what a severe geomagnetic storm can do arrived in March 1989, when a coronal mass ejection triggered currents that collapsed the Hydro-Quebec transmission system. Six million customers in the province lost power for nine hours. That blackout demonstrated how geomagnetically induced currents, or GICs, can saturate transformer cores and trip protective relays across an interconnected grid. The Congressional Budget Office documented the event as part of its assessment of North American grid security, noting that mitigation options exist but require upfront investment to harden the system.
The 1989 storm, however, was far weaker than the Carrington Event. In 1859, the geomagnetic disturbance was intense enough to set telegraph offices on fire and allow operators to transmit messages on equipment disconnected from batteries. Since then, the North American grid has grown dramatically. Long-distance, high-voltage transmission lines now stretch across thousands of additional miles compared with 1990 levels. Because GICs flow more easily through longer conductors, the effective attack surface for a Carrington-class storm is wider today than it was during the Quebec incident. Satellite-era magnetometer data confirms that the geomagnetic field changes during the 1859 event dwarfed those recorded in 1989, which means the damage threshold for today’s expanded grid sits well below the intensity the Carrington storm actually delivered.
Storms roughly half as intense as the Carrington Event strike Earth on approximately 50-year timescales, according to NOAA. That recurrence rate means the question is not whether a strong geomagnetic storm will hit the modern grid but when, and whether the grid will be ready.
Federal cost estimates and the transformer bottleneck
The $0.6 trillion to $2.6 trillion damage range cited by the U.S. Geological Survey captures direct equipment losses, cascading economic disruption, and recovery costs. The lower bound assumes a storm that damages a limited number of extra-high-voltage transformers in regions with favorable geology, where resistive rock limits GIC flow. The upper bound reflects a scenario in which the storm path crosses regions underlain by conductive geology, amplifying currents into transformers that take 12 to 24 months to manufacture and ship from a small number of global suppliers.
That manufacturing constraint is the central bottleneck. Extra-high-voltage transformers are custom-built, weigh hundreds of tons, and cannot be mass-produced on short notice. A storm that destroys or permanently degrades dozens of them simultaneously would leave affected service territories without replacement hardware for a period measured in months, not days. The USGS fact sheet on geoelectric hazards ties the severity of grid damage directly to the interaction between solar storm intensity, local geology, and the length and orientation of transmission lines, all variables that differ sharply across U.S. regions.
No publicly available federal dataset currently maps the age, shielding status, and geological exposure of every extra-high-voltage transformer in the country. Without that inventory, the spread between the $0.6 trillion and $2.6 trillion estimates stays wide, and grid operators lack a precise picture of which assets face the greatest risk.
Gaps in storm preparedness and what to watch next
Several open questions shape the real-world risk. First, the economic models behind the damage range are now more than a decade old. The NRC published its estimate in 2008; Lloyd’s followed in 2013. Neither analysis fully accounts for the grid expansion, renewable-energy buildout, and increased digital dependency that have occurred since. An updated federal economic model, incorporating current transformer inventories and supply-chain lead times, does not yet exist in the public record.
Second, real-time grid operator responses during moderate geomagnetic storms over the past several years have not been published in a consolidated, primary-source format. Operators in some regions have adopted GIC monitoring and transformer-neutral blocking devices, but no comprehensive federal audit has confirmed how many critical transformers remain unprotected. Without that transparency, it is difficult for regulators and emergency planners to judge whether operational procedures-such as temporarily reducing power transfers during storms-would be enough to prevent permanent equipment damage in a Carrington-class event.
Third, the current solar cycle is approaching its peak. NOAA tracks sunspot counts and coronal mass ejection frequency as indicators of storm likelihood. A strong cycle raises the probability of a severe event occurring before grid hardening measures are fully deployed. The practical gap between known risk and completed mitigation is the central tension for utilities, regulators, and the roughly 300 million people who rely on uninterrupted power for everything from water treatment to medical care.
That tension shows up in several policy debates. One concerns whether to require utilities to install more GIC-blocking devices on transformers that sit above especially conductive rock formations. Another centers on how much spare transformer capacity should be maintained in strategic reserves, given the long manufacturing lead times and limited number of suppliers. A third involves the role of federal agencies in coordinating space-weather forecasts, grid operator alerts, and public communication during a major storm.
Some mitigation work is under way. Utilities in higher-latitude states have begun installing additional monitoring equipment to measure GICs in real time, allowing operators to reroute power flows or temporarily disconnect vulnerable lines when solar storms arrive. Industry groups have also explored mutual-assistance agreements for sharing spare transformers after disasters. But these measures remain unevenly distributed, and there is no single, authoritative inventory that shows which regions have implemented which protections.
For households and businesses, the most visible impacts of a Carrington-scale storm would likely include prolonged blackouts, degraded GPS and satellite communications, and disruptions to fuel and food distribution networks that depend on reliable electricity. Hospitals and data centers with backup generators would fare better than small clinics or local governments with limited reserves. Telecommunications networks, which rely on a mix of grid power and battery backups, could see outages that complicate emergency response.
Looking ahead, several developments will help clarify the true scale of the threat. A modernized federal assessment that updates the 2008 and 2013 economic models with current grid data would narrow the damage range and highlight the most cost-effective protections. Expanded public reporting on GIC events and operator responses during moderate storms would reveal how close the system is to critical thresholds. And as the present solar cycle matures, each near miss-or direct hit-will test whether the incremental hardening efforts of the past decade are enough to keep the lights on when the sun next unleashes a storm in the Carrington class.
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*This article was researched with the help of AI, with human editors creating the final content.
