In the race to roll out cleaner and more fuel-efficient passenger cars and light trucks, automakers appear to have left one cheap, abundant alternative on idle: natural gas.

Clean-energy advocates hope that could change as technology makes it easier to unlock vast stores of the cleaner-burning energy source and as fueling stations become commonplace.

The benefits of NGVs are compelling: Prices are lower than gasoline, and the vehicles produce 20% to 45% fewer smog-producing pollutants and 5% to 9% fewer greenhouse gas emissions, according to the U.S. Department of Energy. At a time when energy independence is just as important as cost, it doesn’t hurt that 94% of natural gas is produced in the U.S.

The emergence of fracking technology has made it easier to drill in shale formations like Marcellus in the Appalachian Basin and Bakken in North Dakota and Montana. This increased production drove natural gas prices to historic lows last year — and even though prices have doubled since then, natural gas remains cheaper than gasoline or diesel.

Those compelling economics are not lost on automakers, which are eager to get a piece of the action. Navigant Research forecasts that the natural gas vehicle market will grow by an annual compound growth rate of nearly 8% to reach 19.9 million vehicles worldwide by 2016. Growth in natural gas refueling stations will be slower, but still will reach nearly 26,000 stations by 2016.

Vehicles powered by natural gas have been around for decades, and have been selling successfully in Europe and Asia (particularly in Pakistan and Iran). But in the U.S., buses and commercial trucks account for the lion’s share of such vehicles.

Honda’s (NYSE:HMC) Civic Natural Gas sedan was the only commercially marketed passenger car at this time last year. Dealers sold about 2,000 of the vehicles.

Light trucks have been the initial play in the U.S., as General Motors (NYSE:GM) rolled out two CNG-powered pickups last year — the Chevy Silverado and GMC Sierra 2500 HD, which can run on gasoline as well.

Fiat’s (PINK:FIATY) Chrysler sells the Dodge Ram 2500 CNG, another so-called “bi-fuel” vehicle that can run on both gasoline and natural gas. And Ford (NYSE:F) is selling retrofitted bi-fuel CNG versions of its F-250 and F-350 heavy-duty pickups.

As is the case with plug-in hybrids and EVs, NGVs are more expensive than gas-powered vehicles. Prospective buyers also struggle with “refueling anxiety” — there are only about 1,000 natural gas fueling stations in the U.S., compared to more than 200,000 service stations that sell gasoline.

Each of those stations costs about $750,000 to build, according to Clean Energy (NASDAQ:CLNE), a provider of natural gas fueling solutions. But if you can find a station, filling up with an equal amount of natural gas is like shaving $1.50 per gallon off the price of gasoline.

Still, for the NGV market to thrive, it will require a lot of public and private sector support. Federal government tax incentives for alternative fueled vehicles and refueling infrastructure apply to NGVs as well; many state and local governments offer tax breaks too.

Last week, for example, lawmakers in Pennsylvania moved a package of grants and incentives aimed at funding NGVs and fueling infrastructure.

The move makes political sense — Pennsylvania is at the epicenter of the Marcellus formation and a big winner from the shale gas boom. Major producers like Exxon Mobil (NYSE:XOM), Chesapeake Energy (NYSE:CHK) and Devon Energy (NYSE:DVN) would benefit from broader use of natural gas in transportation.

But there are at least three barriers to mass adoption of NGVs in the U.S. — lack of fueling infrastructure, attractive price point and vehicle selection, and a long-term price advantage of natural gas compared to gasoline or diesel.

Even if U.S. drivers should transition to NGVs en masse over the next decade, it should have minimal impact on natural gas prices, according to a new study from the American Clean Skies Foundation released last week.

The report found that retail prices for compressed natural gas or liquefied natural gas will remain attractive compared to diesel and gasoline — even if natural gas prices rise significantly.

But these developments are likely to come slowly. ACSF’s most optimistic forecast estimates that natural gas demand from NVGs will only account for 2% of the overall market by 2025.

Bottom Line

Natural gas-powered vehicles are a promising opportunity for automakers and energy companies — government and business vehicle fleets, as well as trucks and buses, already are taking advantage of this clean, abundant energy source. And rich shale gas formations in the U.S. make it more likely that natural gas will remain cheaper than gasoline or diesel for the foreseeable future.

Nevertheless, don’t expect U.S. consumers to convert to NGVs en masse anytime soon. It will take big time and money to establish a robust refueling infrastructure, and automakers have offered U.S. consumers limited choices in NGVs so far (and they’re more expensive than comparable gasoline-powered vehicles).

Consumer adoption of NGVs likely will ramp up slowly over the next few years; but once infrastructure is in place and attractive, affordable vehicles are widely available, automakers should be able to cash in on this source of fuel.

As of this writing, Susan J. Aluise did not hold a position in any of the aforementioned securities.