Originally Posted by Sledge
Phill is for natural gas, not LPG. Phill costs somewhere around $5k
You shouldn't assume that we don't know the difference:
CNG - Compressed Natural Gas
LPG - Liquefied Petroleum Gas (Propane)
Either can be used with conversions in some vehicles. The conversion kits are similar, but the pressure tank for CNG is more expensive (CNG is a less expensive fuel, but there are compression costs as noted earlier).
Both are Greener fuels than gasoline.
As you noted Phill is a low-cost home compressor that accepts natural gas and compresses it into the storage tank of a converted vehicle.
If you want to use LPG, you install a large storage tank in (or near) your home and fill the smaller tank (in the trunk of the converted vehicle) from the stored propane (home delivery is generally available).