On the French version, there are 3 cylinders made of carbon fiber, so that in the event of a crash, they will safely split, and not explode. They meet US safety standards. To completely fill all 3 tanks, takes 4 hours of running a compressor, similar to your standard Sears air compressor. It would certainly be equivalent or less than running my home's AC for the same amount of time. This would be the equivalent of 28% my current gas tank, so as long as it costs less than $28USD to fill all three, it saves money. more info: http://zeropollutionmotors.us/