This work is aimed to analyse environmental impacts of a stand-alone solar-based polygeneration power plant that consists of a photovoltaic panel array, a battery pack, a unitised regenerative polymer electrolyte membrane fuel cell and a diesel backup generator. Life Cycle Assessment was performed for the same plant layout and control strategy applied to a reference commercial building located in different climate zones in the United States. Specifically, Global Warming Potential, Cumulative Energy Demand, Acidification and Eutrophication Potentials were analysed. Results showed the critical impact of manufacturing and use phases, highlighting the significant differences between the contributions of these phases, strongly depending on the plant location, which affects both power supply and demand, while the contribution of the end of life phase was negligible. The environmental impact of the entire system is driven by manufacturing of different units, i.e. photovoltaic panel arrays and batteries. Besides, a sensitivity of the results was investigated to identify the major factors affecting the manufacturing of these components. The unitised regenerative fuel cell was found to have a low impact during its entire life-cycle, and this may suggest increasing its size to reduce or replace batteries and diesel generator, which strongly affect manufacturing and use phases.