President Carter's energy plan will contain mandatory fuel conservation measures, White House energy chief James R. Schlesinger said yesterday.

Legislation to require stricter fuel efficiency in automobiles, stop power plants from burning oil and natural gas, make home appliances more efficent and encourage home insulation are the principal elements of the proposal, he said.

In his first major speech as Carter's energy adviser, Schlesinger told a convention of the National Wildlife Federation here that the need for strict conservation "implies major adjustments in the attitudes and the way of life in the United States."

Schlesinger's outline of the energy message, to be released April 20, followed his revelation to a group of citizens Friday that the Carter administration will abandon plans to develop plutonium fuel for nuclear power plannts in the immediate future.

Plutonium, a heavy gray metal that can be extracted from the used uranium fuel of conventional nucluear plants, is a key ingredient of neclear bombs. Energy officials fear its wide spread use would accelerate the spread of nuclear weapons around the world and encourage theft by terrorists.

"No miracle technologies" will solve the energy crisis, Schlesinger told the Wildlife Federation yesterday.

"By 1990, the world will peak in terms of its capacity to produce petroleum. By the early part of the 21st century we will begin to run out of oil. That will mean drastic changes. It will require radical readjustments on our part."

Schlesinger asked for support from the more than 500 conservationists, saying, "Ecomony in the use of fuel in industry will mean stepping on many toes. To put our comprehensive energy plan across we will need your help. It is difficult for any society to make adjustments in its prior paterns of life."

The White House is known to be seriously considering measures that would force utilities to burn coal for electricity, instead of natural gas and oil. Among these are a tax on gas used as boiler fuel, bringing it up to the price of oil, and legislation forcing conversion to coal unless utilitics can prove they should be exempt.

"We want to get power plants off gas and oil," Schedlesinger told reporters after the speech. "That may require some legislation."

Clean-burning natural gas provides 30 per cent of utility fuel today, and enviromentalists fear coal conversion would aggravate air pollution, Utlities oppose the plan, contending it would cost $50 billion without assuring a long-term commitment to coal.

Schlesinger told the wildlife group that conservation "means a requirement for far more fuel-efficient cars . . . (and that applies) to some of you who like 8-mile-per-gallon recreational vehicles . . . as much as to limousines."

A 1975 law allows continued sale of large cars and campers if enough small, high-mileage cars are sold to meet an overall average of 27.5 miles per gallon by 1985. Carter energy officials are reportedly considering a tax on gas-guzzlers of up to $500 per vehicle and a payment of up to $500 for small-car purchasers - a move which could face stiff congressional opposition.

President Carter made clear in an interview with 29 news executives yesterday that he does not favor a crash program to step up domestic oil and natural gas production - a prime objective of the Ford administration.

Consequently, in addition to conservation and coal, Carter apparently plans to rely on conventional uranium-fueled nuclear power plants. Schlesinger said Friday the administration wants to "seperate the use of nuclear power from the spread of nuclear weapons . . . from the plutonium economy."

Such a policy sugggests the probable demise of the liquid-metal fast breeder reactor, now planned as a demonstration project on the Clinch River in Tennessee, and of any plants to extract plutonium from the spent fuel of conventional reactors.

But the administration would support the building of more uranium-fueled plants, despite enviromental opposition and utilty company fears that uranium supplies will be exhausted in 25 years.

Schlesinger said, however, that the adminstration might "try a different set of breeder technologies" that would not involve plutonium. A breeder reactor would produce more fuel than it consumes.

In his speech yesterday, Schlesinger said conservation is the "keystone" of the Carter program, through voluntary measures or even mandatory measures if they are required - and I must state they will be required." He added later that "voluntary acts have to be reingorced by legislation."

The energy chief told the wildlife group "we must get control over the rate of increase in demand for energy. It has been growing at 4.5 per cent a year, which means that every 15 yers the demand for energy doubles."

Adjusting to slower growth "implies a challenge to the American system," he said. "One of the political risks we face is the danger of balkanization of producer regions and consumer regions, the Southwest, New England and the Midwest which are all in need of energy."

Carter's program "will require enthusiastic support" from enviromentalists, labor unions and business Schlesinger said. "Generating that support will be a demanding task . . . We've had a tendency toward rampant individualism in the past. The energy problem will require a restore consensus before the time of ultimate danger arrives."