President Carter's April 20 energy message will stress energy conservation, reduced government regulation of the energy industry and increased use of coal, energy adviser James R. Schlesinger said yesterday.

Appearing before the Senate Governmental Affairs Committee Schlesinger urged early action on the President's plan to create a new Department of Energy which was unveiled last week.

"We can no longer live with the fragmentation, the duplication, the overlapping jurisdications, and the conflicting mandates evident in the organization for dealing with energy problems," Schlesinger said.

Schlesinger declined to detail the administration proposal for a National Energy policy, which will be released next month. Sen. William V. Roth Jr. (R-Del.) said, "It bothers me that we are structruring a new department with no real knowledge of where you are going."

Congressional and industry sources said they expect Carter will set fuel efficiency standards and call for a national home insulation program.

Schlesinger said the administration would also call for increased coal usage by industry, although he stopped short of endorsing legislation introduced by Sen. Jennings Randolph (D.W. Va.) which would require electicity utilities burnin goil or natural gas to convert to coal.

Stressing a =desire to reduce the regulatory burden" in energy pricing and allocation decisions, Schelesinger said the Department of Energy would streamline regulatory decisions for oil, handled by the Federal Energy Administration, and natural gas, handled by the Federal Power Commission, putting both on an equal footing.

"We hope." Schlesinger said. "to move increasingly over the years to informal regulatory decisions."

Schlesinger did not say which regulations would be eliminated. During the campaign Carter, in a letter to the governors of three oil-producing states, called for deregulation of interstate natural gas prices for at least a five-year period.

The new department, which Schlesinger is expested to head, would be the first one created since the Department of transportation was established in 1966.

The Energy Department would absorb functions performed by the Federal Energy Administration, the Federal Power Commission, and the Energy Research and Development Administration, and would receive energy responsibilities from agencies and departments.

Sen. Abraham A. Ribicoff (D-Conn.) who chairs the Governmenial Affairs Committee, said he expects his committee to send a bill to the Senate floor "by the end of April" after three weeks of hearings.

Ribicoff, in an interview after yesterday's hearing, said he expects "quite a few amendments" to be introduced to the President's bill, including proposals to expand the Department of Energy's powers in international energy matters.

"It is my feeling that the Secretary of Energy should have primary responsibility over international energy policy, as opposed to the Secretaries of State and Treasury," Ribicoff said.

During the hearing Sen. Henry M. Jackson (D. Wash.) said, "I think the record of the State Department on energy is rather miserable."

Jackson, who was one of the senators co-sponsoring the President's energy proposal, is said to be concerned about the administration's coordination of uranium enrichment, proliferation, and nuclear export policies.

Granting the proposed Department of Energy broad powers in international energy policy would represent a major change in the existing government structure. The State Department and to a lesser extent Treasury and the FEA have a tight rein on international energy questions.