Pepco, who isn't equipped to handle it.
About 1,969 customers are without power downtown; however, most of them are north of Union Station (about 1,500). So Penn Quarter has largely been spared, for now.
The space between the two Lexington buildings on 8th Street is an electrical transformer. Lines from there go underground to most Penn Quarter buildings, so we are generally spared from downed power lines. However, overconsumption is a different game.
If you do lose power, there is a "cooling center" located at the Walker Jones Education Campus at 1125 New Jersey Ave N.W.
Many downtown government buildings--federal and local--have been closed because of the power outage, so check first if you're going anywhere downtown.