EVERYBODY FAVORS converting oil-fired power plants to coal. It's a splendid way to cut oil imports. The quarrel, now as always, revolves interminably around the next question: who's to pay for it, and how?

Congress first tried to push the utilities away from oil in 1974, after the Arab embargo. But they are using as much oil now as they did then. Coal generates just under half of the country's electric power; the rest comes, in very roughly equal proportions, from oil, natural gas, water and uranium. In his energy speech last July, President Carter declared that he would seek legislation requiring the utilities to cut their oil consumption in half over the next 10 years. But the administration did not get a firm proposal to Congress until March. Committees in both houses are currently struggling with that central question of cost.

The president's bill names 50 generating plants that would have to convert at a cost variously estimated from $5 billion to more than $10 billion. Twelve of those plants, incidentally, belong to Vepco. The upper end of that price range buys a high degree of environmental protection that would permit the coal to be burned with less pollution than oil. The president thinks that the taxpayer ought to pay for most of it, and his bill would provide $4 billion in federal grants. Those grants constitute a heavy subsidy to both the coal industry and certain consumers. The congressional committees are aware that multibillion-dollar subsidies are hardly consistent with the drive to balance the budget.

Since it's much cheaper to generate electricity with coal than with oil, conversion promises to benefit consumers directly. Isn't it fairer to let those consumers pay for it? But, in many states, the regulatory commissions have effectively blocked conversion. Most of the regulators have been extremely slow and reluctant in granting rate increases to pay for conversion. They evidently prefer to leave the utilities running on oil, where the rising fuel costs get passed along automatically through fuel adjustment clauses. That's less unpopular.

Perhaps the best solution would be to split conversion costs between taxpayers and ratepayers. Congress could offer grants -- although smaller than those Mr. Carter proposed -- contingent on state regulators' passing through, fully and promptly, rate surcharges for those utilities required by law to convert. The amounts of oil to be saved are substantial -- a million barrels a day by 1990, Mr Carter says. As the price of oil soars, the long delay in shifting the power plants to coal is damaging not only the national interest, but the interests of individual consumers as well.