where E anion and E neut are the total energies of the anionic and neutral systems respectively, and E 1e is the ground-state eigenvalue of a single electron in the confining potential of Eq. 1. We found previously that unrestricted MP2 results agreed well with gold-standard Coupled Cluster Singles Doubles and perturbative Triples (CCSD(T)) interaction energies, 9 so we use MP2 as the reference in this work. Density functional calculations were performed in Q-Chem 5.0.2, 40 with the SG-1 Exchange-Correlation (XC) integration grid. Care had to be taken due to our use of a floating Gaussian basis formed with distributed ghost helium atoms that each contributed to XC integration grid centers. As discussed in detail in Supplementary Material Section S-I, SG-1's use of pruned angular grids in atomic core regions introduces large integration errors if a ghost atom is too close to a real atom. To avoid this issue, we removed the ghost atom at the origin, and added its s primitive function to the oxygen atom's basis. We consider first the BLYP functional, since this was used in the first planewave DFT study of e - (aq) . 16 Fig. plots the electron-water interaction energy for three different orientations (indicated by the molecular graphics at the top of the figure). Panel (a) shows the interaction energies for an electron on the oxygen side of water. As expected, the interaction energy is positive, corresponding to a repulsion from the partially negative oxygen atom. However, BLYP (dashed blue curves) sig-nificantly underestimates the magnitude of repulsion by ∼0.2 eV compared to the reference MP2 results (green circles) at high confinement strengths (small e --water distances). Similar behavior is seen in two other orientations: dipole aligned (panel (b)) and OH bond aligned (panel (c)), which show attractive interactions as expected, but with BLYP overestimating the attraction by ∼0.2 eV when the electron is close to the water. The overestimated attraction between the electron and water at short range in BLYP is suggestive of the delocalization error. Indeed, Johnson and co-workers found significant convexity error in the energy versus fractional charge of a Kevan model of the hydrated electron with BLYP, raising the concern that delocalization error is severe when this functional is applied to solvated electrons. We confirm this is the case in Fig. , which plots spin densities for the electron-water system. We indeed see that for all orientations and confining strengths, BLYP (dashed blue curves) underestimates the spin density of the excess electron in the attractive well region and overestimates the spin density on the water molecule compared to MP2 (green circles), with the error most severe at large confining strengths.