Recently, the problem of high electricity prices appeared in household uses, especially in water heating then the use of solar collectors was the best proposed solution to this problem. A computer program is written to predict domestic hot water production using a parabolic trough collector. The proposed system consists of a parabolic trough collector, a circulating system, a hot water storage tank, and a heat exchanger. The program was used to test the effect of three major design parameters. These parameters are mass flow rate of working fluid (0.50, 0.75 and 1.00 kg/m), collector aperture area (1.0, 1.5 and 2.0 m²), and storage tank capacity (50, 75 and 100kg). The study also revealed that the hot water temperature depends on both storage tank capacity and the collector aperture area. It was concluded that a match between the collector aperture area and storage tank capacity must be taken into consideration when designing a solar hot water production system. The proposed system is capable of produce 60-80 °C, which is satisfactory for domestic hot water production with an average efficiency of 51.50% which is considerable higher compared to other solar collectors. It is recommended to be used system under aperture area of 1.00 m² and mass flow rate of 0.75 kg/min with 75 kg for storage tank capacity. Finally, a model validation was conducted by comparing the obtained results to those available through literature survey. A good match was found between the study results and published results.