You're comparing mass to volume in that last paragraph there. Based on a quick google search, that 1 kilogram of hydrogen is going to take up 3.4 gallons as a c

You're comparing mass to volume in that last paragraph there. Based on a quick google search, that 1 kilogram of hydrogen is going to take up 3.4 gallons as a cryogenic liquid—so even more as a compressed gas. Source: http://www.uigi.com/h2_conv.html http://www.uigi.com/h2_conv.html