Potomac Electric Power Company customers in the District of Columbia will pay about $6 million less on their electricity bills -- about $5.40 for the average customer -- over the next few months because Pepco is selling large amounts of electricity to other utilities.

Part of the profit Pepco makes on sales of electricity to other companies is passed on to the company's customers.

During January, Pepco sold $39 million worth of power to other members of the Pennsylvania-New Jersey-Maryland power pool. Much of the power went to Metropolitan Edison, the owner of the Three Mile Island nuclear plants that have been closed indefinitely. A year ago, the pool brought only $5 million worth of power from Pepco.

Pepco yesterday asked the D.C. Public Service Commission to let it supply power to Metropolitan Edison at bargain rates. That would mean lower electric bills for customers who had been served by the Three Mile Island plants but less savings for Pepco's own customers.

The $6 million savings represents the customers' share of profits for January. Additional rebates to customers are expected because the company is selling large amounts of electricity again this month. The savings will be credited as part of the fuel adjustment clause over the next few months.

The heavy electricity sales are expected to slow down in March when the weather begins to warm up.