Photos: Philling up your Honda Civic GX

The Civic GX has a kevlar and carbon-fiber-wrapped fuel tank, which holds the equivalent of 8 gallons of natural gas compressed at around 3600psi. Because of the GX's limited range on a full tank (around 220 miles) and the relative scarcity of public natural-gas filling stations nationwide (around 140), home refueling is an attractive option.

Based on the gasoline-powered Honda Civic, the 2008 Civic GX features the world's cleanest combustion engine, according to the EPA, and is rated as an inherently low emission vehicle (ILEV).

Because of the low flow rate (0.42 gasoline gallon equivalent per hour), a typical refuel using Phill is done overnight. The green LED lights indicate the current level of compressed gasoline in the car's tank. When the tank is full, the system shuts itself off automatically. According to Honda, the Phill system is being monitored with a view to developing the company's Home Energy Station IV hydrogen fueling system, which generates hydrogen from natural gas in order to power a fuel-cell car and to provide electricity for domestic use.

The Phill system requires a dedicated gas line, a separate AC power outlet, and specific venting. Owners are also required to obtain a permit for installation. According to installers of this system, the cost of running a car on CNG works out to about $1.30 a gallon, 30 cents of which goes to the Phill system's electricity running cost.

Manufactured by FuelMaker, the Phill system enables Civic GX owners to fill their cars up with natural gas in their own garages. Phill is essentially a compressor connected to a standard domestic gas supply. It costs between $4,000 and $4,500, exclusive of installation and a Federal tax credit of $1,000. The system must be installed by a FuelMaker-approved contractor.