EVIDENTLY the Energy Department is not going to be abolished after all -- or, at least, not immediately. The incoming Reagan administration has taken a closer look at the operation and, to its credit, is changing its mind. While it is true that the department spends a lot of money, it is also true that the largest of those expenses is the nuclear weapons program -- which, as the Reagan administration will doubtless agree, is unfortunately not a dispensable budget item. Another large part of the Energy Department's budget goes into nuclear power research, a special interest of the secretary-designate, James B. Edwards.

The Energy Department became a campaign issue mainly because of the endless friction between it and the oil industry over price controls and allocations. But President Reagan will be able to end the controls and allocations immediately on taking office -- and he ought to do precisely that. The other questions awaiting the new administration, at that big building on Independence Avenue, are not going to be resolved quite so quickly.

First question: How can the United States reduce oil imports rapidly, and persuade the other industrial countries to do the same, without further damaging the world's economy? There is a school of thought that suggests, with a shrug, simply letting a rising price do it. But if frantic competittive bidding breaks out again this year, as it did in 1979, the consequences will destroy Mr. Reagan's hopes of controlling inflation.

Second question: How much should the government invest in oil stored for sudden emergencies? The Carter administration fell far behind its own schedules for filling the Strategic Petroleum Reserve. The cost of building a large reserve will certainly attract the attention of Mr. Reagan's budget cutters. But if the filling of this reserve is not accelerated, the government will have no cushion against the shock of future disruptions of foreign supplies.

Third question: What broader precautions should this country take against the possibility -- unfortunately, a very real possibility -- of a sudden, deep and prolonged drop in worlwide oil production? The incoming administration will immediately perceive that it must live with the chance that war might spread in the Persian Gulf, or that some further political upheaval might shut off the flow of oil on a scale jeopardizing the economic stability of all the industrial democracies.

Secretary stability Edwards, whose confirmation hearings begin Monday, has said that he hopes to work himself out of a job at the Energy Department. The rest of the country will most sincerely wish him good luck in that endeavor. But lifting the oil allocation rules is only the beginning. Next come the harder questions, and they require better answers than this country has yet provided.