In a policy switch that will make natural gas available to more homeowners and businesses, the Carter administration is urging state utility regulators to ease restrictions on gas use.

States should permit hookups of new residential gas customers and encourage industries and utilities to burn gas rather than oil, according to the latest administration gas policy.

The policy change is expected to make natural gas available for new homes in the Washington suburbs, where Washington Gas Light has been able to hook up only limited numbers of new customers.

With federal encouragement, states have been restricting new residential hookups for several years. Less than two years ago, the Carter administration called on industries and utilities to switch from gas to oil or coal.

The abrupt about-face reflects improved gas supplies -- as a result of conservation and increased production -- and an effort to curtail use of imported oil, said Jerry Peffer, acting assistant administrator of the Economic Regulatory Administration of the Department of Energy.

This week, Energy Secretary James Schlesinger said the nation now has "excess deliverability" of natural gas and called for encouraging gas use.

The word went out to state officials from David Bardin, head of the EERA, who said the federal policy is "to encourage industrial and utility users of middle distilates to switch to natural gas or propane." Middle distrilates include heating oil, the fuel most industries started using when the government told them to stop burning natural gas.

In a letter to state utility regulators, Bardin said the latest policy is meant "to ease dependency on imported petroleum." Oil imports increased because industries switched from gas to oil.

Peffer said the new policy extends to use of gas for home heating and said energy officials have told the states they should ease restrictions on new residential hookups.

Washington Gas Light is preparing to ask Maryland and Virginia regulators for permission to add more new customers.

After a long moratorium on new gas hook ups, Virginia, Maryland and the District of Columbia last year agreed to permit the local utility to add about 10,000 new customers.

The company's quota in Maryland and Virginia has been used up, according to Susan Butz, spokeswoman for the utility. In the District, where there has been less new home construction, gas is still available.

Hooking up more customers here will require the approval of the Maryland and Virginia utility regulators, who appeared yesterday to be laboring under the impression the nation still has a gas shortage.

Both states restrict new connections and have applications pending from utilities that want to add more customers. Baltimore Gas & Electric recently got limited authority to add residential customers, and Virginia Electric and Power Co. is asking approval to add customers in the Tidewater area.

Washington Gas last year got permission to add small business and residential users of 19 million therms of gas a year to its system. The company has used up that capacity in the suburbs making commitments to add 4,000 new customers in Maryland and 2,800 in Virginia, although not all have been hooked up.

In Washington, 600 new customers have been added.

Butz said more than 90 percent of the new residential customers were all-gas homes, with furnaces, water heaters and stoves using gas, which is substantially cheaper than electricity.