Update: Pepco responds.
It seems that approximately 1,900 Pepco customers in Petworth do not have power today due to a "planned outage" performed by Pepco. (See a map of the outages on Pepco's site.) Power is supposed to be restored by 3pm.
According to a Pepco representative, planned outages occur when they need to do work to improve a system, or if there is a situation where they need to fix something and turning off the power is required. These outages are scheduled ahead of time, and the customer service department is notified in case customers call in to report an outage. The representative also said that Pepco notifies customers who have a "medical alert" on their account (those needing electricity for life-saving equipment, etc.).
Apparently, Pepco doesn't need to tell you that you're going to lose power. Their policy is to inform customers only if they call to complain or report the outage.
Work from home? Take care of children? Home sick and want to spend the day on Netflix? Oh well, they don't need to tell you. You'll figure it out once your lights go out. Enjoy the humid silence. Go out to a park, hopefully the rain is over.
This is a great example of when the customer is the least important part of a business.
You can share feedback with their "Customer Advocate" via email. I'm sure they'll get right on it!
(Thanks to Andrew from Borderstan for the head's up.)