The enhancement of passive cooling for a photovoltaic (PV) module in a finned container heat sink was proposed. Palm wax was chosen as a phase change material (PCM) for this research as it was much cheaper than other commercial PCMs. Initially, three different PCM containers, i.e. grooved, tubed and finned containers, were designed and investigated. It was found that the finned container exhibited the best cooling effect. Thus, the PV module temperature was much decreased, giving the highest electrical power output. Then, the passive cooling with the finned container was further analysed and compared to the module without cooling. The finned box could reduce the module temperature from 57.9 degrees C to 51.8 degrees C (a 6.1 degrees C temperature drop). Thus, the module efficiency was enhanced from 9.33% to 9.82%, corresponding to a 5.3% improvement. Also, the averaged performance ratio (PR) rose from 0.63 to 0.66 (4.8% enhancement). It was discovered that palm wax had potential as a PCM capable of cooling the PV module. Importantly, passive cooling of the PV module using PCM was not always beneficial, but depended on the irradiance. The results made clear that when the solar irradiance was higher than 500 W/m(2), there was a great enhancement in the PV performance with cooling. However, there is no need for PV cooling if less irradiance is usually the case.