Computations have been instrumental in the discovery and development of new TE materials. Large-scale computationally-driven discovery of TE materials requires robust and tractable performance metrics or descriptors. Several such descriptors, including the electronic fitness function, Fermi surface complexity factor, and the quality factor have been proposed. In developing these material descriptors, it is typically assumed that the charge transport can be ascribed to a single carrier type (electrons or holes) and, therefore, the TE performance can be described within a single parabolic band approximation. While this is a reasonable approximation for materials with band gaps that are wide enough to avoid significant bipolar conduction, it breaks down in materials where high concentrations of both electrons and holes are present, such as narrow-gap semiconductors and semimetals. Bipolar conduction increases the electrical conductivity while simultaneously decreasing the Seebeck coe cient and increasing the electronic thermal conductivity. As such, material descriptors for predicting the TE performance of narrow-gap semiconductors and semimetals must account for e↵ects arising from bipolar conduction.