Examples of co-added and normalised spectra of the Gaia-ESO Survey. The panels in the first two rows show different wavelength ranges of a spectrum with high signal-to-noise ratio (star 11325994-3151279). Specifically, the first row shows the entire lower (left panel) and upper (right panel) spectra, while the second row shows two smaller portions of the spectrum around the Hβ (left panel) and Hα (right panel) lines. The panels in the last two rows show the same ranges of a spectrum with low signal-to-noise ratio (star 14572655-4056351). At the top of each panel the median of the signal-to-noise ratio per pixel for the spectral range plotted in the panel is provided.