This study examined the economics of a solar water heating system for an office building using life cycle cost (LCC) optimization simulations. The numerical simulations were conducted with TRNSYS and GenOpt employing the Hooke-Jeeves algorithm. The solar collector area, slope, mass flow rate per collector area and storage tank volume were selected as the main design parameters of the solar water heating system. The LCC optimization simulations of the system were carried out for cases where water temperature was $60^{circ}C$ and $50^{circ}C$. The results showed that for water temperature at $60^{circ}C$ and $50^{circ}C$ the collector area could be decreased by 17% and 28%, storage tank volume could be decreased by 49% and 54%, and mass flow rate per collector area increased by 5% and 9% respectively compared to a non-optimized system. The LCC of the system was reduced by 4% for $60^{circ}C$ and 7% for $50^{circ}C$. The initial installation cost of the system was reduced by 24% for $60^{circ}C$ and 34% for $50^{circ}C$. However, the operating cost of the system increased by 16% for $60^{circ}C$ and 36% for $50^{circ}C$ compared to a traditional solar water heating system.