Vertically-mounted bifacial module farms (VBF), which are ideal for power generation projects of traditional industries wherein photovoltaics are applied (i.e., ‘PV +’ mode), have some unique advantages such as extremely high land utilization, anti-fouling ability, and grid peak shaving ability. However, VBF also suffer from shortcomings such as low power generation efficiency and high levelized cost of energy (LCOE). This paper proposes the VBF-bifacial companion method (VBF-BCM) for light supplementation and efficiency enhancement of VBF. A reflective device is added to the PV brackets in the VBF, and supplementary light is applied to the dark side of the module in the adjacent row. The technical and economic feasibility of VBF-BCM were determined and calculations showed that the VBF-BCM system can significantly increase system power generation worldwide. The maximum power generation gain ratio was 90%, and the global annual average was 70%. Compared with the latitude-tilted mounted monofacial module farms (LTMF), the total power generation of the VBF-BCM system can be increased by more than 35% globally. Furthermore, VBF-BCM can reduce the LCOE of the original VBF solution by up to 40%, which renders VBF-BCM a perfect PV system that is ideal for the ‘PV +’ mode