The presented system is used to produce relatively larger amounts of sterilized water than by merely putting a fixed amount of contaminated water in a small bottle inside a hot box solar cooker (HBSC). For achieving a specified temperature with the HBSC, a thermostat attached to a solenoid valve is placed at the outlet port of the HBSC to ensure that the desired temperature corresponds to the water-sterilization temperature. A basic heat transfer analysis is done for the HBSC to find the effect of environmental conditions for the behavior of the system. Thermal and biological tests of the water samples during the sterilization process are obtained. The performance data collected for the systems indicates that there was good viability for solar energy in sterilizing contaminated water.