Hydrogen is not a power source - it has to be generated by cracking water...with extremely large amounts of heat, or with electricity. So we need the high-capacity power plants either way (nuclear to generate the extreme heat for that method, or just any significant power output for the electrolysis method).
Just to be clear (and I'm not saying that you erred), hydrogen
is the power source for fusion. The question involved is whether the power required for isolating the correct isotopes, generating and maintaining ignition temps/pressures plus conversion losses are less than the rate at which can be energy obtained from fusion of whatever amount of hydrogen we can fuse at a time (on average).
Unless of course we uncover some cheap source of ready to burn or nearly ready to burn hydrogen.
Edited by NoNukes, : No reason given.
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