Fusion reactors can use different fuels based on how good they are at containing plasma. Right now, almost all research is directed towards the easiest possibl

Fusion reactors can use different fuels based on how good they are at containing plasma. Right now, almost all research is directed towards the easiest possible fuel that requires least powerful containment, that is, Tritium (H3) and Deuterium (H2). Deuterium can be separated from water, and Tritium can be bred from Lithium using waste neutrons. T+D is inexhaustible, but also quite expensive as both separation and neutron breeding are relatively expensive. However, as a fusion reactor consumes tiny amounts of fuel per unit of energy, a T+D reactor could potentially still run profitably. If we get better at containing plasma, other fuel choices become available. Most important being Boron + Hydrogen, which would be inexhaustible, cheap, and produces minimal neutrons during fusion, making it easier on the equipment. However, free fuel doesn't mean free energy. The cost of all nuclear power, including current fission power, is utterly dominated by the capital cost of equipment.