In this presentation, it will be demonstrated that the combination of soft x-ray and electron spectroscopies (using lab-based surface characterization and high-brilliance synchrotron radiation) can be used to gain insights into the electronic and chemical surface properties of Cu(In,Ga)(S,Se)₂-based chalcopyrite devices for solar water splitting. It will be shown that x-ray and UV photoelectron spectroscopy (XPS and UPS), x-ray-excited Auger electron spectroscopy (XAES), inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive band edge positions, band gaps, work functions, and electronic level alignments. Furthermore, insights into chemical stability can be gained, both with experiments in ultra-high vacuum, as well as under in situ and operando conditions.