SO WHO'S GOING TO RUN the Environmental Protection Agency for the new administration? Perhaps President Carter will answer the question at his press conference this afternoon.It's a matter of some considerable urgency to get that office filled - and all the others that deal with environmental policy. The President is now moving rapidly toward decisions that require a fine balancing of the demands for energy with the constraints of environmental standards.

The energy side of this equation is in the hands of James R. Schlesinger, one of the strongest and most experienced figures in the administration, who was named weeks before the inauguration.Mr. Carter's appointees for the energy jobs, specifically including Mr. Schlesinger, are people with a well informed regard for the environmental implications of their work. But their primary responsibility is energy. Meanwhile the principal environmental agencies are under new appointees who only now unpacking their suitcases or, in the case of the EPA, Republican caretakers who are not in on the meetings where the decisions are being made.

In addition to the crises of fuel supply in this bitter winter, here is a long series of requirements forcing the Carter administration to move fast on energy and environmental questions. For example, the law on automobile emissions has fallen into deep confusion. The EPA is the main repository of the government's expertise on this extremely technical issue. It will take time for the next administrator to get a grip on the issue. In the meantime, the EPA and its resources will contribute little to the legislation that Senator Muskie is vigorously pushing forward.

The new budget process, with its legal deadlines, means that the Carter administration can make only limited changes in President Ford's budget. The energy research budget sets priorities for development, and the Ford administration's first priority was the breeder reactor. The breeder raises a range of serious dangers far beyond the rather remote hazards of the present generation of nuclear generators. It would be decidedly unfortunate if the opposition to the breeder wereexpressed now here within the structure of the new administration before it passes its budget revisions on to Congress.

The people running the environmental agencies over the next few years are not likely to be terribly popular. They are inevitably going to be the nay-sayers at a time when Americans' houses are chilly, and factories are shut for want of fuel. That is all the greater reason why these officials need to be appointed promptly, to enable them to take part in this winter's crucial decisions, rather than arriving only to find that the main lines of policy have already been fixed.