PRESIDENT CARTER'S ENERGY plan is now halfway through Congress, and its' time to take stock. As the legislation now stands, it provides neither a complete strategy for the next eight years, nor any great protection in the interim against foreign disruptions and price rises. The President's plan has one primary purpose: to reduce this country's dangerous dependence on foreign oil. The bill, as the House passed it, does not promise to reduce oil imports. It would only hold down the rate at which things are getting worse. That is the central thought to keep in mind, as the Senate now threatens to throw out large sections of the plan.

The history of this massive bill, over the summer, is interesting mainly as further demonstration of the very narrow limits of political possibility in regard to energy. Most of Congress understands perfectly well the need to cut down. But it is exceedingly difficult to persuade people to make provisions for a shortage of which there is no visible sign yet. There is also great uncertainly among the experts over the effects of rigorous energy conservation on the national economy. With the unemployment rate back up over 7 percent, not many people in Congress are inclined to try anything that might interfere with economic growth.

As it passed the House, the legislation would cut oil consumption mainly by pushing industry and utilities more heavily onto coal as their primary fuel. Most of the rest of the gain would be picked up through conservation. The method is a series of carrot-and-stick devices, mostly imposing higher prices, sometimes accompanying them with tax credits for investing in insulation or more efficient machinery.

The legislation has serious flaws, but some of them were inevitable. It is, for example, far too complex and rambling. But that only reflects the reality that the country has not arrived at any consensus on energy policy. The authors of the bill have attempted, as usual, to splice together various irreconcilable ideas of efficiency and fairness. That can't be remedied. But the Senate is in a position to fix another defect, the lack of strong incentives for new oil and gas production in the United States. The administration drew up the bill on the assumption that it was impossible to raise domestic production much, and a waste of money to try. That rather pessimistic judgment may well prove to be correct, but it deserves to be tested more vigorously than the House bill permits.

The outlook for this legislation in the Senate, unfortunately, is not promising. Last week the Energy Committee voted to throw out the whole section on electricity rates in response to a spurious states'-rights argument. If the senators do not like the tangled provisions of the House bill, they can improve its language. But it is absurd to say that there is no national interest in reforming rates to discourage wasteful and expensive patterns of using power. Beyond that, and much worse, a number of senators are now organizing an attack on the crude-oil tax that is basic to the whole Carter plan. The tax would raise the price of most oil products - including gasoline, but not home-heating oil - by 7 cents or more per gallon over the next three years.

If the crude-oil tax is defeated, there will be little left in the energy program but a slow-moving effort to push industries into greater use of coal. The Carter plan has consistently underestimated the difficulties of a widespread expansion of coal production and use. Shifting oil-fired industrial boilers to coal is a necessary part of a national energy plan. But, by itself, it is very far from adequate.

For all of this shortcomings, the House energy bill is a creditable and, you could even say, courageous attempt to meet a national danger that is genuine. The chances of working out a better bill next year are very poor, since 1978 is an election year. If the Senate now throws out large pieces of the bill, the effect can be measured in increased vulnerability of the American economy to the shocks and surges of a radically unstable world oil supply.