A method was proposed to predict the performance of a solar powered desalination unit used to provide water for a drip irrigation system to grow bell pepper under greenhouse conditions, and evaluate the economical prospective of such system. The results showed that the method could be used successfully to predict the performance of the desalination unit. The results indicated a strong correlation between the predicted and the measured values with a R² value of 0.96. The water use efficiency (WUE) value was 8.2 kg/m³ and the final product unit added cost was 17.1 LE/kg.