A new report from the Federal Energy Regulatory Commission shows that as little as nine terrorists could take out the United States’ electrical grid for as much as 18 months.

The report says that on a hot summer day, a coordinated attack on just nine of the nation’s 55,000 electric-transmission substations would cripple the system to the point it would cause a nationwide blackout.

“This would be an event of unprecedented proportions,” Ross Baldick, professor of electrical engineering at the University of Texas told the Wall Street Journal.

The article in the WSJ comes a day after a report from a New Jersey utility oversight committee showed a serious lack of security at key electrical substations.  The report also cited the April 2013 attack on a Pacific Gas & Electric transmission station that knocked out 17 transformers with shots from sniper rifles.

The memo from the FERC says the California attack shows “it does not require sophistication to do significant damage to the U.S. grid.”