Residents of the Washington area and much of Maryland may face higher electricity bills in the near future as part of a utility industry plan to help out the utility that operates and is part owner of the crippled Three Mile Island nuclear power plant in Pennsylvania.

Both Potomac Electric Power Co. and Baltimore Gas and Electric Co. have filed petitions with Washington area public service commissions, asking the agencies to declare that it is in the public interest to alter the rate structure for power sold to Metropolitan Edison.

If the plan is put into effect, the move could cost Pepco's residential customers as much as $9 per house-hold this year.

The plan is being promoted by the utility industry in Pennsylvania, Delaware and New Jersey as well as Maryland and the District of Columbia. d

The proposal must first gain the approval of the state agencies and then the Federal Energy Regulatory Commission.

It would let Pepco and Baltimore Gas sell excess electricity to Metropolitan Edison, the operator and 50 percent owner of Three Mile Island, At a reduced rate.

This would shift some of the burden for higher oil and coal costs to local customers, whose fuel adjustments would increased. Changes in the fuel adjustment factors of monthly bills do not require prior regulatory agency approval, and Pepco has estimated that its customers could face new costs of up to $4 million in 1980.

Brian Lederer, the people's counsel at the D.C. Public Service Commission, said yesterday that the Pepco proposal "raises questions about the validity of fuel adjustment clauses" since customer rates could be altered by such a new pool sales agreement.

"This would be a transfer of income from rate payers here to [General Public Utilities] to help bail out GPU," he said.

One of the two nuclear generating stations at Three Mile Island was shut down last March after the most serious nuclear power production accident in history. The second plant has remained closed.

General Public Utilities Corp., owner of Metropolitan Edison, has estimated that the costs of buying outside power to replace the Three Mile Island capacity will be $345 million a year.

After consultations with the Pennsylvania Public Service Commission, other regional state regulatory agencies and electric companies that form a power pool called the Pennsylvania-New Jersey-Maryland Interconnection (PJM), the new rate structures was proposed as a way to reduce by up to $30 million a year the cost of the extra power that General Public Utilities must buy.

Edward Mitchell, a senior vice president of Pepco, said his company and other companies in the pool, including Balitmore Gas, have simply "offered relief to GPU's customers. . . It is a help." But he emphasized that if what was termed a "possible arrangement" is not approved by state agencies, the agreement will be dropped.

Asked last night whether customers of Pepco and the other utilities are being asked to subsidize Metropolitan Edison, Mitchell replied: "We would hope that our customers would understand the reasons for this. . . . If they object, if the commissions say this is not a good idea, that's it."

Lederer, the people's counsel, also said:

"You can always justify things in the short run and maybe it is in the best interest of the public that we don't let GPU go bankrupt. . . but there is a lot of money at stake. It's an example of things beyond regulatory control."

The D.C. commission yesterday scheduled a prehearing conference on the proposal for Jan. 28 and will accept comments from interested parties before the date.

Pepco's Mitchell said last night that, in exchange for the proposed $30 million rate cut for Metropolitan Edison, the other utilities required General Public to place funds in escrow every week to cover purchases "so we would be assured of getting a greater proportion [of funds due] if GPU defualts." In addition, if GPU goes bankrupt, the company would lose all voting rights and control of the power pool.

In another development yesterday, General Public said it will form a separate corporation to operate the company's nuclear facilities, including Three Mile Island. GPU president William Kuhns told the Pennsylvania commission that the new corporate plan would help upgrade safety management.