Atomistic simulation techniques have been used to investigate the energetics of defects and dopants, of oxygen migration and of proton incorporation in BaCeO3. The calculations suggest that the concentration of intrinsic atomic defects is quite low even at relatively high temperatures. Under reducing conditions, BaCeO3 seems to contain oxygen vacancies and conduction band electrons and thus exhibits n-type conduction. Furthermore, trivalent dopants at the Ce-site have favourable solution energies, particularly Y, Yb and Gd. Oxygen ion migration is found to have an activation energy of about 0.85 eV, which is consistent with experimental values. We have calculated the energy of incorporation of water in BaCe1 -xYxO3 - delta and found it to be increasingly exothermic as we increase the Y3+ concentration.