The solar-assisted heat pump (SAHP) is considered to be one of the most efficient and promising heating electrification technologies, while the research on improving its energy efficiency at night is insufficient. In this study, an innovative solar assisted heat pump and building integrated thermal storage/PV system (PV-SAHP-TS) was proposed to upgrade the heating efficiency during night-time and those periods when solar radiation is insufficient. Four building pilots were selected for installation to measure both the impact of different climate conditions on the integrated system energy and the economic performance after adopting this strategy. The pilot buildings were located in Nottingham (UK), Valladolid (Spain), Mafra Municipality (Portugal) and Peristeri Municipality (Greece), with warm, mild-temperate and slightly cold climate types, respectively. The SAHP system was working during the day to improve both electricity generation and solar heat extraction. The PV renewable electricity was used to support the compressor of the SAHP system in the full load operation. The water thermal storage tank was used to charge heat in the daytime to release at night-time. To investigate the annual operation performance of the proposed integrated PV-SAHP-TS system, hourly dynamic simulations in EnergyPro were conducted. The simulation results indicated that the hybrid heating COP could increase from 3.4-3.6 (SAHP alone) to 6.2-9.2 (integrated system), with net electricity savings of 27%, 50%, 57% and 61% in the four pilots, respectively. It was noticed that this proposed strategy could help reduce the peak electricity load by a maximum of 73% due to the thermal storage in the daytime. Besides, in the summertime, the system could operate independently without power input from the electrical grid.