VALLEY FORGE, Pa. (WTVN) -- Operators of the power grid that serves 13 states and the District of Columbia are warning customers to reduce their electric usage this evening or there may be rolling blackouts.

Record usage of 138,600 megawatts was set Tuesday morning, breaking the old record from February 2007 of 136,000 megawatts. It's only a 2 percent increase, but PJM Interconnection spokesman Ray Dotter says that's still a lot of power.

"That's the equivalent of about three major power plants, so think of three nuclear plants that would be required to make up that increase," Dotter said.

PJM expects to break the record again this evening.

"We're expecting that the peak of usage that we see this evening, probably around 7 or 8 o'clock, will be higher than it was this morning," he said.

The strain on power generators has caused some to trip offline. If power conservations don't work, rolling blackouts could be required.

"It is a possibility that, sure, but it's what we work to avoid," he said.

Dotter says they're asking customers to put off using things like dishwashers, clothes dryers, and other appliances not needed. Also turn off any lights you don't need to have on.

(Photo courtesy Getty Images)