This paper presents an energy system that utilizes solar energy to produce air conditioning with an absorption refrigeration system. Since there is often a temporal variance between the availability of the required solar energy and the demand for commercial building air conditioning, a liquid natural gas (LNG) subsystem is often used to supplement the solar-thermal array system. Because of operating cost consideration, this paper proposes the use of a R-123 heat pump to supply the required additional heat and temperature needed to effectively operate the absorption air conditioning system. Waste heat from the absorption system water condenser is used by the R-123 heat pump subsystem evaporator to supply the additional required heat at the appropriate temperature to the absorption system generator using the R-123 heat pump subsystem condenser. Under conditions when the pricing ratio of electric power and LNG is at certain level or when LNG is not available, the proposed R-123 heat pump subsystem offers a cost effective option. The solar-thermal collector array and R-123 heat pump are in a series just before the generator of the absorption system. The temperature differential between the absorption system water condenser temperature and the required absorption system generator temperature is relatively moderate, so that the coefficient of performance of the R-123 heat pump subsystem is sufficiently high to be a competitive alternative when compared to a LNG assist subsystem. Because of this moderate temperature difference, the proposed R-123 heat pump assist subsystem appears to be a better choice under certain conditions, than the use of LNG to raise the solar-thermal array transport fluid temperature to the required generator temperature when the solar-thermal array system fails to do so.