Excitation and kinetic energies of prompt-fission fragments are predicted by considering a renormalized Fermi-gas model (RGM) and the concept of the potential-energy surface (PES). Our RGM treats the residual nuclear interactions as energy corrections on the free-gas Fermi surface. The ground-state RGM corrections of the fragments over those of the fissioning nucleus give directly a part of the fragment excitation energy and reproduces the shape of the prompt-neutron yield curve. The remaining part of the excitation is obtained from the change of the deformation-dependent part of the PES evaluated at the scission point. The total energy released in fission is also found from the PES. The kinetic energy is estimated from the conservation of energy. All predicted energies agree well with experiments in the thermal-neutron-induced fission of U235 and Pu239. © 1970 The American Physical Society.