Combining the S, σ , κ el and κ latt allows us to predict the figure of merit ZT as a function of doping level and temperature (Eq. 1) For n-type π SnSe, an industrially-viable ZT > 1 can be obtained at T as low as 300 K, and ZT ≃ 3 comparable to state-of-theart experiments on orthorhombic SnSe 14 can be obtained at high temperature (Fig. ). With n = 4 × 10 19 cm -3 we predict maximum ZT , ZT max , of 1.6 and 2.4 for n-type π SnS and SnSe, respectively, close to the orthorhombic Pnma → Cmcm transition temperatures of 878 and 800 K 71 (Table ). These are larger than the ZT max of the p-type Pnma phases predicted by similar calculations, and very similar to the n-type ZT max (Table ). Larger n = 10 20 cm -1 improve the limiting electrical conductivity and PFs of the π phases, yielding significantly improved ZT max of 2.2 and 3 at these temperatures. Both the Pnma and π phases are predicted to show superior performance with n-type doping, but the differences are much larger in the π phases, with p-type ZT > 1 only attainable at high T and large n (Fig. , Table