The paper reviews salient findings about the conduction band minimum (CBM) in TiO2 and SnO2, which are relevant to applications in energy conversion and storage. The CBM is essential for rational design of an electron-selective contact of the negative electrode in perovskite solar cells. Furthermore, the CBM position controls the performance of dye-sensitized solar cells, anodes of Li-ion batteries and various reductive photoelectrochemical reactions, such as reductions of H+ and CO2. This review is selective rather than comprehensive, and points also at open points and contradictions in the field.