True, Hydrogen has a far higher energy density than li-ion batteries (~150x). But that doesn't show the entire picture. To store and use that hydrogen, you also need a very strong tank (cause of the high pressure it has to be stored in a vehicle) and a fuel cell stack to generate electrical energy. Taking the example of Toyota's Mirai, the hydrogen tank weighs 90kg to just store 5kg of Hydrogen (at 700bar). And this is despite being made of very expensive carbon fibre. If it was made of cheaper but heavier materials like steel, it would weigh much more. And the fuel cell in Mirai weighs 60kg just to output 114kw (155hp). Add all this up and it is a much more even (~2x, not ~150x) comparison with Li-ion battery (for reference Model 3 battery weighs 480kg). And given all this, not surprising the Mirai weighs (1850kg) more than a Model 3 long range (1725kg) despite having similar range and being far less powerful.