Interstate pipeline companies predict they will have much less gas to deliver this winter than they had last year, and gas shortages across the nation may be worse as a result, the Federal Power Commission said yesterday.

A report prepared by the FPC staff and based on data from 50 interstate pipeline firms estimated that deliveries during the 1977-78 heating season would be 169.9 billion cubic feet, or 2.9 per cent, below actual deliveries last winter.

It took a record cold spell last winter to bring on the natural gas shortage that caused many industries and schools to close down and threw thousands of workers out of a job.

But the FPC said even normal weather this coming winter will result in interstate pipelines being unable to deliver some 2 per cent of their wholesale customers' "firm requirements" for natural gas. The shortage last winter was 21 per cent.

The FPC said the most severe curtailments will include the systems of United Gas Pipe Line Company, Transcontinental Gas Pipe Line Corp. and Arkansas Louisiana Gas Co. It predicted shortages on those lines would range from 38 per cent to just over 48 per cent. Transco serves Maryland and Virginia.

The actual impact of the shortages will depend on the weather, the nation's economic activity, and the ability of gas-burning installations to switch temporarily or permanently to other fuels.

Natural gas supplies started declining around 1971 and the situation has grown steadily worse since. The shrinking supply has created on increasing gap between the amounts of gas the pipelines promised their wholesale customers and the amounts actually available.

Shortages haved developed each winter, but were minimized during the winters of 1974-1975 and 1975-1976 by unusually mild weather.

The FPC reported that last winter's firm requirements for natural gas totalled some 7.24 trillion cubic feet but only 5.715 trillion was available, leaving a gap of 1.52 trillion, or 21 per cent.

This coming winter, firm requirements will drop slightly to about 7.2 trillion cubic feet, but available supplies will drop even more - to about 5.54 trillion. This will leave a shortage of some 1.66 trillion cubic feet or 23 per cent, the FPC estimated.