True but the volumetric energy storage density of CNG is about 4 times that of a lithium battery, and 9 times that of NiMH. As I commented to Thackney, electron wells are in short supply.
You can charge a CNG cylinder, store it for a year and it will still have the same charge. You can vent it completely, store it virtually forever, and it will still be just as usable. Low operating temperatures will not degrade range with CNG anywhere near near as badly as it will using batteries.
As I said upthread - CNG works, electric cars do not,
so be assured the left will push electric cars over CNG.