In an unusual confrontation between Washington's two big utility companies. Potomac Electric Power Co. is fighting Washington Gas Light Co.'s request to start taking on new customers after a five-year moratorium.

Charging that WGL's plan is contrary to national energy policy and confusing to consumers, Pepco has filed objections with utility regulators in Maryland and the District of Columbia.

Because of shortages of natural gas, Washington Gas Light stopped hooking up new customers in 1971. In October, the company said its gas supplies had finally caught up with demand and asked permission to add 10,600 new residential and small-business customers. Maryland began public hearings on the request this week and Virginia and the District are expected to do so soon.

Since the moratorium on new gas hookups, the vast majority of new homes in the Washington area have been heated by electricity - supplied by Pepco in Washington and the Maryland suburbs.

In Northern Virginia, Virginia Electric Power Co, is not opposing WGL's plan to resume gas hookups. Nor has Pepco which has only 2,500 Virginia customers, filed objections in that state. But at a hearing in Baltimore Wednesday and in petitions filed in the District, Pepco strongly criticized the gas company.

"WGL's proposal is contrary to the National Energy Act's purpose to promote a shift to coal or other more plentiful and permanent energy supplies," pepco said. About 80 per cent of Pepco's electricity is generated from coal.

The electric company also charged that hooking up additional gas customers "may have significant impact on both the availability of natural gas to existing customers and the conduct of experiments in utility rate design to promote energy conservation and the efficient use of scarce energy resources.

"Expansion of service may lead consumers of doubt the very existence of supply shortages of natural gas, undercutting the credibility of government and the utilities in their efforts to educate the public concerning the energy situation," pepco continued.

"WGL's proposal to further expand demand for limited natural gas supplies by adding new customers and providing additional service to existing customers could contravene the gas and oil conservation goals of the president's energy policy," Pepco complained.

A Washington Gas spokesman said that the company is "surprised they are stirring up such a fuss over such a limited program."

The proposed new hookups - 3,000 in D.C., 4,300 in Maryland and 3,300 in Virginia - amount to only 2 per cent of WGL's business and would not all come into use immediately.

The spokesman said WGL "has an obligation to serve the area as long as gas supplies permit it," noting that the supply of natural gas has stabilized since 1972, and is now increasing slightly.

Since that time, the gas company has lost 7,000 customers due to Metro construction, urban renewal and other demolition. The new customers would bring WGL an estimated $5 million a year in additional revenue.

Because the new hookups would be "restricted to the highest-prioity customers - homes and small businesses - we think it might ease the energy demand on other suppliers," said the WGL officials."

Pepco contends, however, that it is wrong to heat homes with limited supplies of natural gas when there is plenty of coal available to supply electric heat.

Since the moratorium on new natural gas connections, the number of all-electric homes served by Pepco has increased by almost 150 per cent from 9.150 in December 1972 to 22,550 last month.

The trend in residential heating is toward electric heat pumps "which are just as economical as gas," said Pepco president W. Reid Thompson.

"We have no animosity toward Washington Gas Light," said Thompson, but he argued that the electric utility can more efficiently meet local heating needs.

The additional heating customers have helped level out demand for Pepco's energy, which peaks during the summer air conditioning season. During the winter, costly Pepco generating plants sit idle, and the fixed costs of those plants still goes into utility bills, Thompson explained.

Pepco's electric rates are lower in the winter than in the summer to encourage electric heating and to increase winter electrical demand, he noted.

District of Columbia People's Counsel Brian Lederer said he was not yet decided what position to take on the WGL request. It will be at least the first of the year before the D.C. Public Service Commission makes a decision on the question.

In Maryland, hearings on the issue began Wednesday with Washington Gas spokesmen presenting their side, but there was not time for all objections to be heard, a spokesman for the state PSC said. Another day of hearings has been scheduled and a decision probably will be made before Jan. 1, he said.

Virginia utility regulators said the only objections there to added gas hookups have been petitions from Fairfax and Prince William counties. They aruge that if there is enough gas for new customers, there is enough gas to allow gas lights to keep burning. The state has announced its intent to forbid gas lighting.

Virginia already has eased its restrictions on new gas connections compared with the other jurisdictions. Several downstate Virginia utilities have obtained permission to connect enough new customers to maintain their total number of clients. Lynchburg Gas recently was given permission to add 500 new customers.