Abstract: The solar-assisted direct-expansion PVT (photovoltaic-thermal) heat pump is a novel and efficient technology to utilize the solar energy comprehensively. The simulation model of the solar-assisted direct-expansion PVT heat pump hot water system on Matlab platform was developed based on the energy balance, and the effect of the varying environmental conditions and different configurations was investigated. Based on the data of environmental conditions in Lingang, we simulated the hot water supply performance of the systems with different configurations on typical days in different seasons, besides the year-round variation of the electricity generation benefits. The COP of the hot water system increases with the decreasing theoretical displacement of the compressor, however, the needed heating time of the system increases; the year-round electricity generation benefits decrease when the theoretical displacement of the compressor decreases.