We have evaluated the performance of 14 quantum chemistry methods (3 semiempirical methods, 3 DFT functionals, 4 DLPNO CC, and 4 canonical CC) to predict the activation energy of the ozonide. Figure shows how the electronic energies calculated with the 14 methods, using single point calculations with the reference structures from Wheeler et al. , deviate from the reference value of 14.2 kJ•mol -1 . Deviations vary substantially for the 3 semiempirical methods from -83.6 kJ•mol -1 with GFN2-xTB to 0.08 kJ•mol -1 with PM6.