The present paper first presents a comparison between the photovoltaic four-parameter and five-parameter models. The comparison was performed using polycrystalline and amorphous silicon solar cells. The results showed that the four-parameter model can accurately determine the I–V characteristics of single- and polycrystalline solar cells. On the other hand, the five-parameter model can be used to accurately determine the I–V characteristics of amorphous solar cells in addition to its capability of predicting the I–V characteristics of single- and polycrystalline solar cells. Secondly, the economic feasibility of photovoltaic-powered solar water heating systems in Kuwait has been examined. The system includes photovoltaic arrays instead of solar collectors used in common solar water heating systems. The five-parameter model was used to simulate the performance of amorphous silicon modules used with the photovoltaic-powered solar water heating systems. Oil prices in the range of US$20–30 per barrel were studied. At the current prices of photovoltaic modules and a low oil price, photovoltaic-powered solar water heating systems were found to be economical. On the other hand, assuming a low oil price, the price of photovoltaic modules should be reduced to 50% of their current prices to make photovoltaic-powered solar water heating systems feasible in the Kuwaiti climate.