A FEW DAYS ago President Carter sent letters to 300,000 people asking their views on energy policy.L Strangely, we haven't got ours yet. Some people might interpret that as a deliberate slight, but we prefer to regard it as a mere inadvertency. With characteristic generosity, we prepared to overlook the omission and offer Mr. Carter a few suggestions anyway.

American energy consumption is rising much too fast, and Mr. Carter has to decide how much he can slow it down. The trend in energy consumption is steadily upward, at about 3 per cent a year. That trend would mean a doubling of this country's demand for energy by the end of the century. Since domestic oil and gas production are not going to increase, it would further mean something on the order of a 400 per cent increase in the energy drawn from the only two other possible sources - coal and nuclear reactors. That won't work. The costs, both in money and in environmental damage, would set off a public revolt.

If Mr. Carter's target for energy growth is anywhere near the present 3 per cent, it will be a cop-out. But at the other extreme he can't hold it zero because the population is growing - and it's growing fastest in those age groups, in the late teens and early 20s, in which people get their driver's licenses and set up separate households. But the lower Mr. Carter can set his target, the more impact his program will have - and the more benefits it will promise in future conservation and economic stablility.

The same thing is true of the oil import target. It's got to be a great deal lower than the present 10 million barrels a day - which represents nearly half of our current oil supply. Imports at that level leave the country dangerously vulnerable to threats and embargoes. It is the steady uncontrolled rise in American imports that has created a seller's market for OPEC, the exporters' cartel, and helped to hold it together.

But next comes a very hard question: Once Mr. Carter has set his targets, how does he move toward them? Nothing can be done without raising prices. But the whole process of restraint can't be left to higher prices alone.For one thing, nobody knows how high the government would have to lift the price of gasoline in order to enforce the cutbacks that the country needs. Other kinds of intervention are going to be necessary. Perhaps, for instance, it will be necessary to put a flat ban on the sale of any automobile that can't meet a basic national standard of miles per gallon.

A good deal of concern has been expressed for the effects of higher fuel prices on the poor. But the sudden and large price increases also work real hardship on people well up into the middle income range. It's all very well to tell people that they shouldn't have bought those inefficient big cars, or moved way out into the suburbs, or organized their daily lives around the automobile. But they made those choices at a time when the experts - in government, in industry, in academia - were telling them that there was no need to save fuel.

That, it now turns out, was dead wrong. Americans, we suspect, understand the necessity of changing old habits to protect the nation's properity. But it's not going to be comfortable. It takes time to adjust. You might put it this way: A lot of the burden is going to have to be borne by the family that went deeply into debt to buy a new house way out beyond the Beltway, and can't afford to trade in its eight-cylinder station wagon this year. Mr. Carter's energy targets will be curcial, but they need to be targets for the long haul. It's not the oil saved this year that counts most, but the oil saved year after year in a steady trend for decades to come.