CNG cars can even be refueled at home using a device that connects to a house's natural gas lines. That gives motorists even more independence from the filling station, though Questar's pass-through subsidy makes fuel cheaper at one of its stations.

Environmental, tax benefits

Emissions from CNG vehicles are dramatically lower than gasoline or diesel vehicles. "Gasoline pollutes when they refine it, when they put it in the truck, when the truck puts it in the gas station's tank, when it's pumped into the car and when it's burned in the engine," Larsen said. "When you look at the full cycle of pollution, the difference is huge."

Federal environmental policy is the foundation for a number of alternative-fuel tax credits.

Consumers who buy a new vehicle that runs only on natural gas qualify for a $4,000 tax credit. Utah will kick in another $3,000 in tax credits through its own program. The "gotcha" there is that the only vehicle that qualifies is the Honda Civic GX, and in Utah, only Ken Garff Honda downtown sells them, further limiting the supply of qualifying vehicles. The CNG Civic sells for about $25,000. Minus the tax credits, the price is about $130 more than the Civic's gas-engine counterpart.

Tax credits are tied to the vehicle, not the owner, so potential buyers in Utah should check with the Division of Air Quality, which issues tax-credit certificates for CNG vehicles, before buying to see if a particular vehicle is still eligible for the credit.

Ford and Chevrolet were in the CNG market for some time, making factory conversions to fleet-oriented vehicles: vans, pickup trucks and only two passenger cars — the Chevy Cavalier and Ford Contour. Consumers didn't show enough interest, and both manufacturers were out of the CNG business by 2005.

A supply of used bifuel vehicles, which run on either gasoline or natural gas, is available if buyers are willing to do their finding online or shop at government-surplus auctions. Additional tax incentives are available for vehicles put back into commercial use. The Utah Tax Commission says the biggest surge in CNG-vehicle popularity is in the consumer market.

State bureaucrats have had mixed experiences with state-level tax incentives. "In Arizona, nothing was happening with their program so they kept sweetening the pot. Then they went too far and they got hammered," said Utah Air Quality engineer Ran Macdonald. Arizona offered a 50-percent credit on the price of the entire vehicle, which prompted the clever to pay for conversions on Hummers and motor homes and then get half of the entire purchase back from the state.