We present predictions for the dissociative photo- and electroproduction of light and heavy vector mesons off protons. The computation is based on the energy-dependent hot-spot model which incorporates geometric fluctuations of the target-proton partonic structure in the impact-parameter plane. We observe a striking feature of the dissociative cross section as a function of the center-of- mass energy of the photon-proton system. The cross section presents a maximum, whose position depends on the mass of the vector meson and the virtuality of the exchanged photon. By using the positions of these maxima, we define a geometric saturation scale. We find that this scale grows linearly with energy as a function of the scale of the process and we discuss the possibility to map this scale experimentally with respect to the kinematical reach of the proposed electron-ion colliders, JLEIC, eRHIC, and LHeC. This contribution presents results published in Phys. Rev. D 99, 034025 (2019).