Modeling of H₂O SLEDs of quasar host galaxies. Top panels: colored diamonds are the observed H₂O line luminosities normalized to the H₂O 3₁₂ − 3₀₃ line as a function of the energy of the upper level (E_up). The green filled circles are the best-fit models obtained by using our MOLPOP-CEP grids. The best-fit parameters are reported at the top-left corner of each panel. The reported uncertainties take into account only statistical errors ignoring any systematics. Both the E_up and the normalized L_H2O are reported in linear scale. Bottom panels: MCMC output posterior probability distributions of free parameters. The contour plots show 1-σ and 2σ confidence intervals. The same intervals are reported in the marginalized distributions.