The performance of different TiO2 coatings is compared for the photocatalytic inactivation of dry Bacillus subtilis spores dispersed on TiO2 films under UV-A radiation. Three different TiO2 coatings were assayed: Degussa P-25, sol-gel, and composite sol-gel/Degussa P-25. The influence of the increase in the number of TiO2 layers was also studied. Furthermore, the amount of TiO2 deposited on the borosilicate glass plates and the fraction of energy effectively absorbed by the catalytic films were determined. Spectral diffuse transmittance and reflectance measurements were performed using a spectroradiometer with an integrating-sphere attachment. The net-radiation method was then applied to evaluate the fraction of energy absorbed by the coatings. To objectively compare the performance of the catalytic films, two types of efficiencies were calculated: the photonic efficiency and the quantum efficiency of inactivation. The highest quantum efficiency was obtained with the TiO2 Degussa P-25 coating with two layers.