A comprehensive coupled thermal-optical model is developed in MATLAB to predict the performance of a flat plate collector (FPC) and matching its hot water supply with demand of a typical household. The developed model is validated with outdoor and indoor experimental results. The validated model is extended to weather data of a semi-arid climatic condition of Lahore, Pakistan. Monthly and yearly optimum tilt angle is found by selecting its value where FPC gives maximum efficiency throughout the day. The thermal performance of the FPC is evaluated at one clear day of each month for a fixed flow rate to determine its outlet temperature at maximum efficiency. A variable flow rate is also determined for maintaining a fixed outlet temperature. Furthermore, an analysis of demand and supply is carried out. The analysis shows that the efficiency of the FPC remains between 70% and 77% for six hours (09:30 and 15:30) in all months for a fixed flow rate. The flow rate variations in the range of 0.01 kg/s to 0.1 kg/s can maintain a fixed outlet temperature of 50 degrees C. It is also found that the FPC with a variable flow rate can meet the demand of a typical household by employing 8 collectors connected in parallel.