Once your subscription is initialized, your utility bill (BGE, Pepco, etc.) will show a credit each month, based on the amount of electricity (kWh) you consume and the utility’s going price of supplying and distributing that electricity.
So, you will pay less to BGE. But you will get a separate bill from Neighborhood Sun, for that credited amount, minus a fixed percentage discount (generally 5% to 10% depending on the solar farm you joined.) The percentage discount is guaranteed for the life of the contract with Neighborhood Sun, so if BGE’s rate per kWh increases, your discount in dollar terms increases, too.