EVIDENCE KEEPS piling up to demonstrate that Americans are getting more careful in using energy. Currently the country is using less electricity than it did a year ago. That s a remarkable departure from past patterns. Perhpas this dip will turn out to be only temporary. But the longer it goes on, the better for everyone.

For more than two decades, through the 1950s and 1960s, the use of electric power rose steadily at a rate of more than 7 percent a year. At that fierce pace, the generating system had to double its capacity every 10 years and the utilities were under great pressure to build plants as fast as they could. Meanwhile, the price of electricty to consumers steadily declined. But those trends all broke in the early 1970s. There was an oil crisis, prices moved up sharply and a severe recession followed.

Then, after 1975, things seemed to be sliding back torward the old habits -- almost, but not quite. For a time, demand for electricity rose at about 5 percent a year. Then, beginning around last June, the demand for more power slackened. One reason has certainly been higher prices and another, in recent months, has been the mild winter. But there seems to have been a little more to it than that. The change appeared just about the time of the gasoline shortage and the lines at the filling stations. People cut down on their driving and, evidently, on other kinds of energy consumption as well.

One effect has been to reduce the need for imported oil. That's immensely important. But there's another large benefit. Rapid expansion of the generating system brings with it many kinds of risk and pollution about which Americans have properly become increasingly concerned. Generating plants have to run on oil or coal or uranium. Oil imports must be reduced. Nuclear power is never entirely safe. Coal smoke is poisonous. It's a hard choice among them. But if the need for electricity rises only very slowly, the choice is less hard.

This country used only about 1 percent more electricity over the past year than in the previous one. If that low rate of increase can be maintained, few new generating plants will be needed except to replace old and obsolete ones. Since the new plants are cleaner and safer, it is possible to foresee a steady reduction of environmental risk from power production. But that will require continued care -- not stinginess, just care -- in turning switches on and, especially, off.