However, there are some big trade-offs involved in driving a Civic GX. Acceleration is poor, with 0-60mph times coming in at 12.6s according to Edmunds. The range is limited compared to a gasoline powered car, or a Chevy Volt, typically around 200 miles. And if you want to fuel at home, which is likely because CNG stations are not common, you need to install a CNG compressor which will cost you around $5000, installed.
Does the Civic GX make more sense than a Chevrolet Volt? It's a tough call. The Volt's price (after subsidy) is around $33,000. The GX price is about $30,000 if you include the cost of the CNG compressor. For the extra $3,000 you gain the ability to fuel anywhere (if you run it on gasoline or charge at 110v). CNG miles cost about $.07, while all-electric miles will cost you about $0.06 per mile.
But the Volt gets to 60mph in about 8.5s, and in range sustaining (gas) mode has a range of over 300 miles. I think while the government tax credit is in place, I'd take the Volt.