Time resolved microwave conductivity (TRMC) measurements show that the presence of Au on anatase Hombikat UV100 significantly reduces the lifetime of mobile electrons formed by photo-excitation of this photocatalyst at 300 nm, providing evidence for the widely acclaimed electron localization effect of Au in promoting TiO₂ photocatalysts. Electron localization efficiency of Au was even higher for Au-promoted Hombikat calcined at 400 °C, explained by enlargement of the anatase particle size and the associated, relatively larger fraction of anatase particles in direct contact with Au.