EVER SINCE the Arab oil embargo six years ago, the attractions of coal have been obvious. OPEC doesn't control the supply. The United States has vast reserves. It's far cheaper than oil. Experts, forecasters and presidential commissions -- not to mention the coal industry itself -- keep calling attention to its possibilities. One recent example is the World Coal Study, published last week by an international group based at the Massachusetts Institute of Technology. It declares that world coal production will have to increase 2.5 to 3 tiems by the end of the century with the largest expansion here in the United States. But that is not happening, and is not likely to happen. The reasons are worth examining.

The principal use of coal is to generate electricity. In this country, the utilities' demand for coal is running below expectations because their customers' demand for power is running below expectations -- sharply. Americans are currently using less electricity than they did a year ago.The last year-to-year drop was in the industrial lull at the end of World War II. Since then, it's been a rapid upward curve. But now that curve has been broken by the impact of higher prices and by conservation.

Two common errors run through most of the energy forecasts of the past six years, including the World Coal Study. There has been a strong tendency to overestimate economic growth rates and to underestimate possibilities for conservation. The result has been a pattern of excessively high estimates of future fuel and power requirements.

Burning coal is risky. A massive increase in coal consumption would bring with it certain substantial hazards to health and the environment. Most of these hazards can be successfully controlled with intricate and expensive technology. But to some -- for example, the large volume of carbon dioxide emitted into the atmosphere -- there is no answer yet. The use of coal is going to increase over the coming years here and around the world. But there is every reason to burn no more than absolutely necessary.

How much is absolutely necessary? With the disappearance of cheap oil, people in every country are now rapidly developing ways of maintaining economic growth through far more efficient use of less fuel. On present evidence, they are making progress. The progress is sufficiently rapid that they are unlikely to have to triple, over the next 20 years, the amounts of coal being burned on this planet.