Compliance with the new Clean Air Act may be a costly burden to electric utilities, factories and coal producers, but it looks like money in the bank to the natural gas industry.

Converting power plants from coal to natural gas and developing fleets of cars and trucks that run on natural gas instead of diesel fuel or gasoline could increase demand for natural gas by as much as 13 percent above current levels by the year 2005, according to studies released recently by the American Gas Association (AGA), the principal industry trade group.

With natural gas prices hovering near their historic lows because of weak demand and the relatively mild winter, AGA officials welcomed the Clean Air Act as a light at the end of their tunnel, despite some recent reports questioning the industry's ability to find new customers and to deliver gas to all who might want it.

AGA Chairman William T. McCormick Jr., chief executive of Michigan-based CMS Energy Corp., and AGA President Michael Baly III said the demand for gas will vary according to the choices made by individual utilities about how to bring their plants into compliance with the new law.

Many of the utilities that operate the 110 coal-burning power plants required to reduce emissions between the years 1995 and 2000 have longtime relationships with coal producers in their states and are expected to install "scrubbers" on their plants so they can continue using high-sulfur coal. But McCormick said the others are "free to use the most cost-effective option," which he said will be natural gas.

The Clean Air Act also requires that owners of vehicle fleets in the nation's 22 smoggiest metropolitan areas purchase low-emission or clean-fuel vehicles, beginning in 1994.

In addition, President Bush is expected to propose in his forthcoming national energy strategy that owners of most commercial vehicle fleets be required to switch to fuels other than gasoline beginning in 1995.

Cars and small trucks powered by compressed natural gas are common in other countries and increasingly available in the United States, and they represent a logical choice for fleet owners, said McCormick and Baly. At present, most of the U.S. vehicles that can run on natural gas are "dual fuel" -- able to run on either natural gas or gasoline -- but automakers are developing "dedicated" natural gas engines. Fleet owners that can provide a central tank-filling point will be the target customers, at least until natural gas becomes widely available to individual motorists at conventional service stations.

Amoco Corp. recently opened the first compressed natural gas filling pump for Washington-area motorists at a Capitol Hill station.

Some potential natural gas customers are still leery of the fuel because they remember the shortages of the 1970s, when natural gas prices were regulated.

The U.S. Energy Information Administration and the latest annual issue of "Natural Gas Trends," published by Arthur Andersen & Co. and Cambridge Energy Research Associates, warned recently that new investments in drilling, pipelines and storage facilities will be needed if the gas industry is to meet demand.

Baly said that natural gas is plentiful now that it has been deregulated, but he acknowledged that customers "are asking about deliverability" -- the availability of pipeline capacity to move that abundant natural gas from wellhead to retail customer.

Baly released an AGA study showing that more than 8,000 miles of new pipelines, costing more than $8 billion, are under construction or have been approved.

Benjamin Schlesinger, an independent natural gas consultant in Bethesda, said the AGA demand projections are "reasonable because there is going to be a lot of demand for gas under {the} Clean Air {Act}."