Despite predictions that the United States will begin running out of natural gas before the turn of the century, gas utility companies are stepping up efforts to get new customers.

Industry estimates are that 550,000 new natural gas customers were hooked up in 1977 and roughly that many will be added this year.

That's about 40 percent more new gas customers than in 1976 and the most since 1972, when most state utility regulators restricted new gas connections in response to the emerging energy crisis.

Some new industrial gas users are being hooked up, but most of the new customers are homes and small businesses, the highest-priority users of natural gas under federal rules.

The gas industry "has a tough marketing job to do to convince people we're going to have in 20 or 30 years," admits Frank Rock, president of Lynchburg Gas, a small Virginia utility that recently obtained permission to take on new customers.

"The federal government has convinced the American public we are running out of gas," he complained. "They're making it very difficult for us."

The utility companies insist they will have gas to burn for the next 200 years, even though the American Gas Association estimates present domestic reserves will last 30 years.

The industry is counting on massive imports of gas from Algeria and Mexico, new gas wells in Alaska and offshore in the Atlantic Ocean, gas extracted from coal, and gas that hasn't been discovered yet to supply the customers they are getting now.

Whatever Congress does about deregulating natural gas prices, these new supplies will cost more than the gas homeowners are burning now; imported liquified natural gas costs up to three times as much as price-controlled, domestically produced gas, and both Alaska and off-shore gas are costly.

The gas industry's supply predictions assume these higher cost fuels can be averaged into the prices paid by consumers, and that Congress will permit massive imports. Industry critics are challenge both assumptions, although there is no organized opposition to hooking up new residential gas users.

Connecting new customers is vital to the long-term future of the gas utilities, which lost thousands of customers and millions of dollars in business because of restrictions on adding new customers.

The gas utility industry faces a futher loss of business from proposed federal bans on burning gas as a boiler fuel or to make electricity, and from proposed user taxes that would make industrial gas customers pay as much for gas as they do for competing fuels.

The federal Department of Energy has not taken a stand on new gas connections, but "there's no good reason why new residential hookups should not be allowed," a spokesman said.

"There remains an absolute shortage of natural gas, but within that situation, we're rather see natural gas used for home heating than for anything else."

The closest thing to an official pronouncement on federal attitudes toward new connections came from Charles Curtis, chairman of the Federal Energy Regulatory Commission, the agency that replaced the Federal Power Commission.

"Gas which has been and can be made available through ccnservation and other measures should and must be used for high-priority load growth, where the requirements of existing and new high-priority users can be adequately pro [TEXT OMITTED FROM SOURCE]

In the absence of action by the Energy Department, state regulators and local utility companies have been making the decisions on new natural gas use.

The restrictions have eased steadily. Only Ohio, Kentucky and the District of Columbia now have general bans on new connections, and all three jurisdictions allow some exceptions.

An American Gas Association study indicates new gas connections are restricted in about 40 per cent of the country. The States of Florida, Idaho, Mississippi, North Dakota, Vermont and Utah allow unlimited gas connections, the AGA said.

Other states are allowing new customers to be hooked up if local utility companies can show they have the gas to serve them. Dozens of the nation's 500 gas distribution companies recently have received permission to resume hookups or have applications pending.

Washington Gas Light Co. has asked the District of Columbia, Maryland and Virginia to allow it to add 10,000 customers, ending a five-year moratorium. A Washington Gas Light subsidiary, Shenandoah Gas, has obtained permission to add customers in Martinsburg, W.Va., and has started the hookups.

The gas utilities in Lynchburg and Roanoke already are hooking up new customers with the permission of the Virginia State Corporation Commission.

In New York, Brooklyn Union Gas Co. is taking on both residential and industrial users with virtually no restrictions on their size, and Consolidated Edison wants to add customers.

New gas connections in Southern California alone - most of them houses - accounted for at least 10 per cent of last year's 550,000 new connections, said Dean Hale, editor of Pipeline and Gas Journal.

His estimates of the pace of new hookups are based on a survey of the 500 gas distribution companies that the Texas-based trade publication has taken annually for the last 12 years.

He said some utilities are adding customers to make up for business they have lost in recent years and others are doing so because of improved gas supplies.

One of Illinois' biggest utilities, Northern Illinois Natural Gas, last year asked permission to take on new customers of all kinds, without restrictions. It backed off when the adequacy of its gas supplies was challenged, and settled for permission to connect small customers who had been on a waiting list.

An end to Ohio's moratorium on new connections has been asked by East Ohio Gas, which serves the Cleveland, Akron and Youngstown areas.

Ohio has faced more severe natural gas shortages than most states because of its heavy concentration of industrial gas users, which are at the bottom of the priority list drawn up by the old Federal Power Commission.

The Ohio utility probably will get approval for new gas connections if it can show its supplies have improved, said an official of the Ohio Public Utilities Commission.

Supplies vary from one utility company to the next, depending on the kind of customers they have and their source of gas. Some pipeline companies or gas wholesalers have more gas than others. Some gas companies have been able to arrange to import gas, while others have manufactured gas from petroleum products or have bought gas outside the normal pipeline channels.

Overall, "There are at least 30 years of conventional U.S. gas supplies remaining at the present consumption rate," the American Gas Association said in a report released last month.

Making a plea for deregulation of natural gas prices, AGA said "more realistic federal regulatory policies . . . will assure U.S. natural gas production at current levels an additional 15 to 20 years."

After that, foreign supplies will be needed to fuel the U.S., which consumes nearly half of the world's annual natural gas production of 48 trillion cubic feet.

The gas industry estimates known natural gas reserves at 2,200 trillion cubic feet, and another 7,500 trillion cubic feet have yet to be discovered, "resulting in a remaining resource life at the present consumption level in excess of 20 years."

Even if gas consumption were doubled, world supplies "would be sufficient to sustain production at or near this level for at least another 50 years," the industry group says.

The AGA's estimates of available world gas supplies were made as part of its pitch for unrestricted imports of liquefied natural gas, or LNG. In order to transport gas by ship, it must be frozen and compressed to one six-hundredth of its normal volume, a process that can triple the price of the fuel.

A more detailed explaination of where the gas to serve new customers will come from is shown by Washington Gas Light's petition for new customers.

Ajit S. Ratra, WGL's senior engineer for corporate planning, has presented the company's arguments in Maryland and will testify this month at a hearing in the District of Columbia.

Ratra discusses gas supplies in terms of "millions of decatherms," or MDth. A dekatherm is a million BTUs of heat from gas.

He said Washington Gas Light's two primary pipeline suppliers, Columbia Gas Transmission Corp. and Transcontinental Gas Pipeline Corp., say that for the 12 months starting last November they can supply 119,792 MDth.

During this year, the company's customers will need 116,365 MDth and the customers the company wants to add would use another 2,024 MDth.

"The available supply is more than adequate to meet these requirements," Ratra said in his Maryland testimony. Projections show "an increasing surplus of available supply over the projected requirements," he asserted.

Because Washington Gas Light has lost about 7,200 customers due to building demolition and other attrition, the company is saving 158 MDth a year. Energy conservation will trim annual demand by another 3,436 MDth.

Columbia, the main supplier,says its gas wells in the southwest United States, which now supply 73 per cent of the gas used by local consumers, will contribute only 20 per cent of the supply in 1985.

Columbia plans to begin importing LNG from Algeria this spring, using its Cove Point, Md., terminal. By 1985, Algerian gas will supply about 6 per cent of Columbia's gas, and LNG imports from other countries will be slightly more than double that.

Atlantic offshore wells that haven't been drilled yet are being counted on for about 3 per cent of the gas needs, and natural gas production in Alaska, scheduled to start in 1984, will supply 9 per cent.

Additional production from present suppliers and deliveries from gas fields that already have been explored and are now being developed will supply 20 per cent of the need.

Another 6 per cent is expected to be supplies by current exploration, and future exploration is being counted on for 15 per cent of the gas burned in 1985.