Energy Secretary Charles Duncan said yesterday he will meet with representatives of 27 major home heating oil suppliers to discuss supplies for the winter and encourage them to hold the line or prices.

Duncan, in his first press conference since becoming secretary, said his expectation "is that the supply situation will be satisfactory" and he expressed confidence "we will get some good responses" at next week's meeting to President Carter's request that the suppliers freeze heating oil prices.

"With the supply situation as good as I think and hope it will be, with the companies exercising moderation on prices," Duncan said it will not be necessary to reimpose price controls on heating oil.

Asked whether the five-cent-a-gallon increase in refiner margins between January and July represented "moderation," Duncan only replied that the Economic Regulatory Administration, a part of DOE, is preparing a report on margins and a public hearing on them will be held Sept. 26.

Standard Oil Co. of California, Chevron, promised the administration yesterday it would moderate the upward trend in its heating oil prices. Earlier, Texaco had said it would freeze through December unless it experienced unexpected cost increases.

Duncan cautioned that all such promises were heavily dependent upon the world supply situation. He said developments in oil producing nations around the world are such that "we will continue to have fragility of supply."

In other matters, Duncan announced an expected reorganization of part of his department and came down hard in favor of expanded use of nuclear power.

"I think that nuclear power will have to continue to play a very substantial role," he declared. "I am a proponent of a more substantial use of nuclear power."

Duncan said that the issue of nuclear waste disposal "is something I am going to give very high priority attention to."

And he added he expects the report from the presidential commission investigating the accident at the Three Mile Island nuclear plant will help clear up nuclear safety issues.