Using the Galerkin variational method, we find the radial wavefunctions of the endohedrally confined hydrogen atom as an expansion on a B-splines basis set. They are used to compute the static dipole polarizability of the hydrogen atom as a function of the confining shell potential, for the ground (1s) and the first two excited (2s and 2p) states. Owing to the avoided crossings observed between the s states (as reported by Connerade et al (1999 J. Phys. B: At. Mol. Opt. Phys. 32 L29)), the polarizability exhibits numerous structures. It is also found that the confinement may increase significantly the electric response of the atom.