In this work, experimental measurements of the electronic band gap of low-k organosilicate dielectrics will be presented and discussed. The measurement of bandgap energies of organosilicates will be made by examining the onset of inelastic energy loss in core-level atomic spectra using X-ray photoelectron spectroscopy. This energy serves as a reference point from which many other facets of the material can be understood, such as the location and presence of defect states in the bulk or at the interface. A comparison with other measurement techniques reported in the literature is presented. © 2014 AIP Publishing LLC.