The natural resources required for the operation of fusion power plants are -with the possible exception of the neutron multiplier beryllium -readily available. On the other hand, the supply of helium, which is required as cryogenic medium and coolant, may be a problem due to losses during operation and decommissioning. Helium is a rare element obtained as a by-product in the extraction of natural gas. The danger exists that the natural gas will be used up without the helium being conserved. We estimate the helium demand for a global 30 % base-load contribution of fusion to electricity supply and also calculate the amount produced by the power plants themselves.