It's now taken for granted that there will be some form of new tax on energy if President Reagan and Congress ever get together on a compromise package to reduce the unprecedented and frightening budget deficits that face the nation in the years ahead.

It's being justified as the "safest" deficit-reducer among a batch of controversial proposals that include, as well, increases in personal income taxes, reductions in military spending, and a less generous cost-of-living adjustment in Social Security benefits.

The simple fact that any of these measures is being considered is an implicit acknowledgment that the original blueprint of Reaganomics has failed--an implicit acknowledgment that makes it politically difficult for Reagan to come to terms with what has to be done.

The deficits have gotten out of hand. The new Brookings Institution "National Priorities" volume puts the red ink at $230 billion for fiscal 1985--requiring, according to Brookings economist Charles L. Schultze, "a $150 billion fix" to avoid a financial catastrophe.

That's a chilling number. My personal view is that neither the White House nor Congress will actually face up to that reality. But I also fear that in a desperate search to recover what was given away last year in the biggest and most inequitable tax cut in history, some stupid things may be done.

One would be to lay on a new energy tax that not only will be inflationary and dilute whatever anti-recessionary benefits may flow from the July 1 tax cut installment, but will work a severe hardship on the poor, already bearing the most severe impact of Reaganomics. If it's the safest revenue-booster, that's because the poor don't have a powerful lobby.

Untold numbers of families struggled through recession and a severe winter to meet home heating bills. Because the poor spend $1 out of every $4 in income on home heat (five times the national average), some of them actually have had to choose between eating and heating. Does this sound like an exaggeration? Listen, then, to a Philadelphia physician, Philip R. Trommer, responding to an earlier column of mine carried by the Philadelphia Inquirer:

"The service man (responding to my request for emergency service when the thermostat dropped 10 degrees in one hour last January) said: 'Yes, you used $1,000 worth of oil in three weeks, but you're lucky, at least you can pay for it.

" 'But we have feeble, elderly people living on Medicaid, and they don't have the money for oil--it's heat or eat.'

"Patients have told me the same thing. What with inflation, shopping centers closing, the need to take buses (or cabs to prevent mugging), sleeping in their clothing, no baths--treating them over the phone with the good graces of a druggist (antibiotics, cough medicines, aspirin) until they thaw out. If they spend money for heat, they don't have enough left over to eat. It's just as simple as that."

Dr. Trommer's example is graphic, but not unusual. The National Consumer Law Center of Washington, in reporting the same "heat vs. eat" phenomenon nationwide, estimates that annual deaths from hypothermia may now be running in the neighborhood of 25,000.

Now, on top of an original Reagan budget that squeezed the poor, including the elimination of all funds to "weatherize" low-income homes, Democrats and Republicans alike are debating a new energy tax, just in time to zap them again next winter.

An energy tax, especially a duty on imports, is seductively attractive. It can raise money quickly, in big batches, and some see it as an opportunity to "stick it to OPEC" at the same time. A $5-per-barrel import fee could raise between $15 billion and $20 billion a year for the Treasury. It would also raise the price of gasoline, fuel oil, food and everything else that depends on oil. Of course, the domestic oil industry would love the price-boosting effect of an import fee, which would fatten its profits, even after a windfall tax.

As Philip Verleger of Booz Hamilton has pointed out, such a fee is strange medicine for an economy in recession, would add a new competitive disadvantage to American exports with an oil component--and do precious little to solidify an already well-entrenched conservation effort.

But the best reason to avoid an energy tax is the impact it would have on the poor. Reagan and Congress gave away too much money to corporations and to upper-bracket individuals in 1981--and that's where they should get it back.