The objective of this study is to analyse the impact of the thermal energy storage system (TES) in the life cycle assessment (LCA) of a concentrating solar power plant (CSP) with central receiver technology. The study uses a base case of a plant with 110 MWel and 17.5 hours of direct storage with molten salts. First, this plant was compared with a plant of equal power but without storage. Subsequently, the LCAs of four plants with different thermal energy storage capacities, 3, 6, 9 and 17.5 equivalent hours, were compared. The results show that TES is key for solar thermal plants, not only to guarantee dispatch capacity, but also to reduce their environmental impact. Comparing different thermal storage capacities, the most environmentally efficient plant of those analysed is the one with a storage capacity of 9 h.