The major challenges to designing high-performance TEs is navigating the space of interlinked physical properties that need to be optimised. In this context, all four of the quantities in the ZT equation are amenable to first-principles calculations, allowing, in principle, the ZT to be estimated as a function of the extrinsic carrier concentration ("doping level") and temperature through a fully ab initio approach. In particular, a recent approach to modelling electronic transport properties including a model for the electron relaxation times, when paired with established approaches to modelling the κ latt , has been shown to yield very good predictions for the well-characterised tin chalcogenides SnS and SnSe and has been applied to study novel candidate TEs including the ternary oxide Bi 2 Sn 2 O 7 and the quaternary oxysulphide Y 2 Ti 2 O 5 S 2 . This type of calculation can provide valuable guidance to experiments as to the conditions where the maximum ZT is likely to be obtained and thus define potential application areas for a material.