LOS ANGELES -- With the future of gasoline prices uncertain, cars and trucks that run on compressed natural gas -- fuel that's about half the cost of gasoline -- are getting another look.

But there aren't many vehicles to choose from. For the moment, Honda Motor Co. is the only major automaker selling natural gas passenger cars in the United States.

Honda, which makes the compressed-natural-gas-powered Civic GX in Indiana, has sold a record number so far this year. Although the volume was small -- 643 -- it was almost triple the number sold during the same period a year earlier, and the company expects to run out of the cars this summer as it gets ready to sell a larger, redesigned version this fall.

The current version gets the equivalent of 24 miles per gallon in city driving and 36 mpg on the highway. The next-generation vehicle is expected to have better fuel economy.

Honda wants to double annual production to at least 2,000, depending on parts availability from earthquake-stricken Japan. The cars list for $25,490 and are sold at 139 dealers in 33 states. Honda plans to certify more dealers to service and sell the cars this year, pushing it into more regions that have natural gas filling stations, Honda spokesman Eric Rosenberg said.

Many drivers install filling stations in their garages, connecting a natural gas pump to their gas piping. But the pump costs about $6,000, minus a $1,000 federal tax credit for the purchase of a natural gas vehicle home refueling system.

Alan Mulally, chief executive officer of Ford Motor Co., said natural gas technology hasn't caught on domestically because automakers find it too difficult to make a cost-competitive passenger car with the trunk space and interior that consumers expect. Compressed gas storage takes more room in a car than conventional gasoline tanks.

Although they don't currently sell natural-gas passenger cars, General Motors Co. and Ford both have CNG offerings in the truck and cargo van segments. Chrysler Group LLC said recently that it plans to develop natural gas vehicles for the U.S. market.

Compressed natural gas emits less carbon dioxide than gasoline when it is burned, and about 85 percent of the compressed natural gas used in the United States is produced domestically.

Still, the fuel is not without critics. A number of states are looking at whether drilling practices to free the gas from rock formations can contaminate water tables.

First Published May 20, 2011, 4:25 a.m.