For completeness, we also present timings for RI-SAPT0(HF)/jun-cc-pVDZ calculations on (guanine) n stacks extracted from an idealized structure of B-DNA. Timing data are presented in Fig. , for calculations in which (guanine) n-1 is treated as a single monomer. For the post-SCF steps, we obtain an effective scaling of O(N ) that is better than the theoretical result. For the system sizes considered (up to n = 6), however, the SCF time constitutes a significant fraction of the overall time, resulting in an effective scaling of O(N 3.1 ) for the entire calculation. For the same systems and basis set, XSAPT + MBD calculations afford effective scaling of O(N 2.6 ) for both the overall time and the post-SCF time, demonstrating that this approach does actually reduce the effective scaling, relatively to RI-SAPT0, even when super-theoretical scaling is obtained. Moreover, the memory footprint of XSAPT + MBD is much smaller.