NIF doesn’t use magnets. Pure inertial confinement. You’re thinking of Tokamaks. Those use superconducting magnets. Superconducting magnets like ITER uses don’

NIF doesn’t use magnets. Pure inertial confinement. You’re thinking of Tokamaks. Those use superconducting magnets. Superconducting magnets like ITER uses don’t require energy to continue running as they, of course, are superconducting. They “only” have to dump heat put into them by the reaction radiation. The SPARC reactor by MIT is similar but much smaller by using Cuprate superconductors (high temperature superconductors, but here operated at much lower temperatures to increase the critical field) that allow much higher field strengths. They often have non-superconducting joints which cause a (sort of) small amount of additional heat that needs to be dumped, but it is possible to make such joints superconducting as well. Anyway, all such designs for commercial scale power from Tokamaks use fusion generated electricity to power the magnet cooling, and those electricity requirements are less than the electricity produced.