The Oil Drum

Here in NZ we once had a thriving CNG industry. Low oil prices and poor installations killed it off and most of the equipment went to Sth America and Pakistan. I have done dozens of conversions and offer the following observations.
Heavy cylinders are a drawback, as is the room they take up. Filling stations would need to be spaced about every 150 kms on major highways. The energy required to compress the gas is usually electric, and we can expect those bills to continue going up. Small vehicles are not suitable for conversion (space,payback and power loss). There is a loss of power. CNG delivers approx 70-80% of petrol power. This is overcome slightly with technical add ons. Maintenance of ignition systems (plugs leads etc) is critical. Far less crap comes out the exhaust pipe. Exhaust systems last longer.

From my POV the most effective way to use CNG is to power public transport like buses with it. Many local councils in NZ used CNG to power their bus fleets. They had their own refilling stations until the "free" market ideology took over and forced the councils to become competitive business units, or whatever the buzzwords of the day were.
When you are ready to start installing CNG send the SOS to NZ as most of the installers here are now in our fifties and apprentices can do the heavy lifting. A team of two could do two cars a day on average, if they were common vehicles. Most of the horror stories came from crap installations done by cowboys. Common problems were starting difficulties, Stalling in windy conditions, Backfiring when starting, poor placement of regulators, problems with icing-up of regulators, did I mention poor starting? All were the result of poor installations and put many people off.
CNG performed best in the old big Six Holdens Fords and Valiants. It was also very good in trucks and buses, but in all cases there was the range issue.
Cheers