Having established that we can consistently obtain converged results, we next turn to computational efficiency. The cost of fragmentation methods is not always discussed honestly, and should be measured in aggregate computer time rather than wall time. Timing data for single-point energy calculations on COMT are provided in Fig. , with the corresponding numerical data in Table . In the absence of any supersystem correction, MBE(2) with PCM boundary conditions costs about 60% as much a supersystem calculation at the same level of theory (ωB97X-D/def2-SVP), whereas MBE(3) is about 14× more expensive than the supersystem calculation. Despite using larger fragments, the charge-coordinated MBE(3) calculation is actually about 10% cheaper than MBE(3) with single-residue fragments, because the former calculation reduces the number of unique subsystems from 7,175 to 3,581. This balance would likely shift in favor of the single-residue calculation if a method more expensive than DFT were used, provided that good fidelity is maintained.