WE WANT TO talk to you this morning about your gas bill--not the one you got this month, but the one you'll begin getting in the late 1980s. There's a lot of gas underneath Alaska's North Slope, and getting it down here to customers in Washington and throughout the country is going to require the longest, most expensive pipeline ever built.

You need to be aware that the cost will be in the range of $40 billion and that it will ultimately be paid by the consumers who use the gas. But to get this assured supply at a stable price far into the future will be worth the money.

Congress now has to vote on it once again. The original legislation five years ago contained restrictions that turn out to make the financing impossible, and President Reagan has asked Congress to waive them. These waivers are a reasonable compromise with the realities of current conditions in the financial markets, and if Congress were to reject them it would, as a practical matter, kill the whole undertaking.

Rejection would also constitute a gross betrayal of the Canadian government, which has permitted the construction of the line south from Calgary into this country on the explicit promise by the United States that the rest of it would proceed promptly. That line is already in operation.

The effect of the waivers is to shift more of the financial risks of this enormous investment from the lenders to the consumers. But those risks are pretty small. The greater issue is the cost of the gas, compared with that of other fuels. At first, that price is likely to be substantially higher. But as time passes, with inflation and the higher oil prices that most people expect, the balance will change. An analysis for the House Energy Committee concludes that, over 20 years, on average, the Alaskan gas would cost slightly less than the alternative fuels. But it's necessary to acknowledge that there are many uncertainties in the calculation. Should consumers have to bear the brunt of those uncertainties?

The greater threat now is further rapid escalation of oil prices--and the higher they go, the better deal the Alaskan gas will be. If the gas at first is expensive and raises your gas bill, you ought to regard it as an insurance premium for the longer future. Whatever happens abroad, the prices of the Alaskan gas will continue to be set by law and by long- term contract. The shorter Alaskan oil pipeline seemed extravagantly expensive when it was finished, in 1977, at $9 billion. But since then it has saved this country $50 billion in the foreign exchange that it would otherwise have paid for more oil from OPEC. For the same reasons, the gas line serves the interest of both the consumer and national security.