The DC public service commission has good resources on choosing a supplier, how to compare rates, and the suppliers available in DC that they have approved. dcpsc.org/Electric/index1.asp
With suppliers you are typically locked into a rate for a 1 or 2 year term and with Pepco prices change every June and November based on the market cost of electricity. The best thing to do is take a look at the suppliers available and then check their websites for current pricing options as compared to Pepco’s SOS rate. There are definitely rates available that are lower than Pepco’s, just watch contract agreements for cancellation fees, price increases, etc.