Top panel: total heating rate as a function of ionisation parameter (ξ) for NGC 1068 (black solid line). The contributions from the different heating processes are also shown: Compton scattering (CS; green dot-dashed line), photoelectrons (PE; purple dotted line), and Auger electrons (AE; orange dashed line). Bottom panel: total cooling rate as a function of ξ for NGC 1068 (black solid line). The contributions from the individual cooling processes are also displayed: inverse-Compton scattering (ICS; orange dot-dashed line), Bremsstrahlung (FF; green dashed line), collisional excitation (CE; purple dot-dashed-dotted line), and recombination (RE; magenta dotted line). Both panels: the labelled circles correspond to the four PION components in each epoch, shown as red for 2000 and blue for 2014, at their respective ionisation parameters from Table 4.