Observed kinetic energy per unit area of the molecular gas (black squares) for NGC 6946. The green area represents the total theoretical energy (E_mod; see also Appendix B) calculated as the sum of the thermal energy (blue band; E_th) and the turbulent energy injected by SNe (red band; E_turb, SNe) with the efficiency η_mol reported on top of the panel. E_turb, SNe is indistinguishable from E_mod, as the thermal energy contribution is negligible.