SBND is a time-projection chamber that collects ionisation electrons and scintillation photons from liquid argon (LArTPC). It will be located 110 m downstream the Booster Neutrino Beam target at Fermilab and it is currently under construction. The SBND physics program is focused on beyond the Standard Model searches (sterile neutrinos, heavy neutral leptons, light dark matter...) and neutrino-argon cross-sections. The photodetection system (PDS) provides trigger capabilities, cosmic-rays rejection (a large background due to the near-surface detector location), and complementary calorimetry. The PDS includes PMTs and X-ARAPUCAsensors, a novel technology that features single photo-electron resolution at cryogenic temperatures with large area coverage in a cost-effective fashion. Proper simulation of the light readout and reconstruction is key for a precise determination of the interaction time (t0) and energy reconstruction, thus improving background rejection. In this talk, we present the latest X-ARAPUCA energy resolution estimates using a full SBND detector simulation. These results are of great interest because future LArTPC experiments such as DUNE will use X-ARAPUCAs as their PDS.