A coordinated, small-scale attack could plunge the US into darkness without too much difficulty, warns a study from the Federal Energy Regulatory Commission (FERC). In certain scenarios, terrorists would be able to take the system offline for months by knocking out just nine key electrical substations around the country. Substations use transformers to help transmit power over long distances and distribute it locally.

The report, which is detailed in a Wall Street Journal article out this week, raises concerns about the safety of the power grid just months after a small group of gunners attacked a substation near San Jose. That incident — which is still under investigation — nearly caused a blackout when the shooters fired at transformers, causing them to leak oil and overheat. The FERC report says that similar attacks, if perpetrated simultaneously on a scorching summer day when Americans are blasting their air conditioners, could be devastating. If the attackers also took out an American manufacturer of power transformers, the power outage could last some 18 months, according to a memo reviewed by The Wall Street Journal.

A coordinated attack could cause unspeakable damage

The nation's power grid is vulnerable for a number of reasons. Numerous reports, including a similar 2012 study by the National Academy of Sciences, have raised alarms about the lack of physical security protecting important substations around the country. The site near San Jose, for instance, was surrounded by little more than a barbed wire fence. But the structure of the US power grid also makes it more susceptible to such an attack. The three main regions — the East, West, and Texas — have limited connections, making it difficult for one region to help another stay online during an attack. Lastly, the custom-made transformers, which increase the voltage of electricity for long range transmission and decrease it for local distribution, are hard to come by and many are produced abroad.

Federal regulation could require power companies to maintain higher security at key substations. Currently, security measures are under the purview of those companies, unless the facilities use nuclear generators. Some lawmakers have expressed interest in such regulation, but implementation of any new rules would take time.