A brief comparative study is presented regarding different exergy efficiency correlations of solar photovoltaic/thermal (PV/T) system that have been proposed in the literature. Performance evaluation results of a certain PV/T hybrid system are found to be inconsistent with each other when using different correlations of exergy efficiency. It is mainly due to that no consensus has been reached in the calculation of thermal exergy, solar radiation exergy and other causal factors. Also, the issues that need to be further investigated are briefly discussed. This study will be beneficial to the design and performance assessment of PV/T hybrid system.