Conceptually, hybrid photovoltaic/thermal (PV/T) system is superior to conventional side-by-side photovoltaic (PV) and solar thermal (ST) system due to the increase of energy output per unit collector coverage area. The current study aims to demonstrate the advantages of applying a liquid-based PV/T system over a side-by-side system in a real office scale building to support its electricity and hot water demand via computer program simulations of the explicit dynamic PV, ST and PV/T system models. Second, an economic analysis considering the time value of money is presented to evaluate the viability of installing a solar collector system with the adoption of PV/T instead of the side-by-side option. The discounted payback period, which has considered the maintenance and parts replacement costs, of the PV/T system design option is found to be encouraging. The sensitivity analysis shows that even under large variations of different factors in the calculation model, positive net present value is dominant in most cases within the analysis time period. The study reflects desirable potential of incorporating of PV/T technologies in real office buildings under subtropical climate region like Hong Kong.