Despite being discovered almost a decade ago, the potential TE performance of the π monochalcogenides has not yet been uncovered, due to a combination of experiments focusing on photovoltaic applications and computational predictions using unsuitable approximations. Among the latter, there are likely few circumstances where neglecting the κ latt in the ZT equation would be reasonable. The Slack model significantly overestimates the κ latt of the π phases compared to solving the Wigner transport equation, although the Cahill model works remarkably well. Finally, unless a reasonable estimate of an electron relaxation time can be obtained (e.g. from experiments ), our results suggest electronic transport calculations within the constant relaxationtime approximation cannot be relied upon for quantitative predictions. On the other hand, the good match between our predicted σ and experimental measurements suggests phenomenological models for the electron scattering may be adequate provided they capture the dominant scattering mechanism(s) (POP scattering for Pnma and π SnS/SnSe).