The aim of this paper was to present a dedicated theoretical investigation into the energy and social economic performance of a novel photovoltaic loop heat pipe/solar assisted heat pump (PV-LHP/ SAHP) water heating system. This involved key structural parameters optimization, operation strategy analyses, energy conservation and environmental benefits analyses and conclusion. The simulation results showed the optimal water tank volume and PV coverage fraction were 150 L and 0.668, respectively. And the suggested operation strategy for the target system is to operate in the PV-LHP mode from 8:00 to 14:00 and run in the heat pump mode after that. With such operation strategy, the net electricity consumption of the optimal system could be reduced by 55.7%, compared to the one with the original design. The annual solar heating fraction and electricity supply ratio were also increased by 7.0% and 26.1%. In terms of energy conservation, the electricity consumption could be reduced by 79.4%. As for environmental benefits, CO2 emission could be cut down by 73.9%. With regard to economic feasibility, the life cycle cost could be saved by 57.3%. The optimal system could have better promising prospect for household application in cold climate area than traditional air source heat pump (ASHP) systems. (C) 2018 Elsevier Ltd. All rights reserved.