We investigated the impact of solvent in model electron transfer and energy transfer photocatalysis reactions. In the case of photoredox catalysis, the PCs that could successfully form the target product were found to photodegrade, and as shown in the pinacol coupling reaction, this occurred regardless of solvent choice. The implication of this observation is that photochemical reactions involving radical chemistry appear to alter the properties of the PC and in these cases, it would be more appropriate to call these reactions photosensitized rather than photocatalyzed. Significantly greater attention should be paid to the photostability of PC in photoredox catalysis as this may explain why some PCs may perform better than others.