The world needs a new source of energy, an unspillable source.

About how much hydrogen would a fusion reactor consume on a daily basis?

I’m not really looking for an exact figure, really just whether it would require very little fuel (like a fission reactor) or a constant flow (like a coal generator). I really don’t understand how a theoretical reactor would work, so I have no idea whether this is even a valid question :P, but any response would be appreciated! P.S. If necessary, assume a desired power output sufficient to power a small city