Most of the primary features contained in these two models are the same. The valence band dispersion, V B C disp , is only contained in M 4,2 , however it does not require any additional calculation because it is extracted from the same band structure as the conduction band dispersion, CB C disp , which is contained in both models. The trace of the molecular polarization tensor, PolarTensor S , is only contained in M 3,3 , however this is a low-cost single molecule feature. Therefore, the cost of evaluating an ensemble model of M 3,3 and M 4,2 is not significantly higher than either model separately. The train RMSE of the high-cost model M 4,3 , 0.10 eV, is slightly lower than the intermediate-cost models M 3,3 and M 4,2 and its test RMSE of 0.22 eV is the same as M 4,2 . H ab is the only primary feature that needs to be calculated to evaluate M 4,3 , in addition to the features already included in M 3,3 and M 4,2 .