It takes out the entire econ

The consequences of going without power for months, across a large swath of the United States, would be devastating. Backup electrical generators in hospitals and other vulnerable facilities would have to rely on fuel that would be in high demand. Diabetics would go without their insulin; heart attack victims would not have their defibrillators; and sick people would have no place to go. Businesses would run out of inventory and extra capacity. Grocery stores would run out of food, and deliveries of all sorts would virtually cease (no gasoline for trucks and airplanes, trains would be down). As we saw with the blackouts caused by Hurricane Sandy, gas stations couldn't pump gas from their tanks, and fuel-carrying trucks wouldn't be able to fill up at refueling stations. Without power, the economy would virtually cease, and if power failed over a large enough portion of the country, simply trucking in supplies from elsewhere would not be adequate to cover the needs of hundreds of millions of people.