The formal scaling of XSAPT is O(N 3 ) when evaluated in the atomic orbital basis and combined with density fitting. Because it requires only monomer-based SCF calculations, XSAPT calculations can sometimes be faster than supramolecular DFT, although the δHF correction and the many-body EDA do require calculations in line with the cost of DFT. Nevertheless, accuracy is improved relative to SAPT0 while cost is reduced.