Pepco has always been the monopoly electric company in the suburbs of Maryland and Washington D.C. but this is no more. Prior to Maryland deregulating the electric utility market you simply paid the rate the regulatory commission decided you should pay rather than letting the free market decide.
Because electric utilities do better on price by competing against each other Maryland as well as many other states has broken up old electric monopolies like Pepco and allowed them to move into other competitive markets as well as let competition into their own market.
Pepco still generates and transmits your electric power to your Maryland home or business but you can now buy electricity and choose from multiple electric rate plans from other providers.
Pepco benefits from Maryland electric choice and deregulation because they can now sell their electricity in other territories and states. If you choose not to go with a competing MD electricity company you will default to Pepco but you now have a choice.
When you choose an alternate MD electric company all power outages will still be handled by Maryland Pepco and there will be no risk of losing electric service for a longer period of time of you move away from Pepco as they are still your pole and wires company.