In this chapter, stationary energy storage systems are assessed concerning their environmental impacts via life-cycle assessment (LCA). The considered storage technologies are pumped hydroelectric storage, different types of batteries and heat storage. After a general introduction to the method of LCA, some methodological implications for energy storage systems and the selection of impact indicators are outlined. Subsequently, the environmental impacts of different energy storage options are assessed in three case studies. The first case study compares pumped hydroelectric storage and utility-scale battery storage applying a screening LCA. Both of the two following case studies are based on an island micro grid application and follow a stepwise approach. The starting point is a pair of cost-optimal energy scenarios – one with and the other without use of stationary battery storage. First, based on the given operational parameters, the environmental performance of different lithium-ion batteries is assessed. This allows the identification of the most appropriate battery chemistry for this specific application (case study 2). Applying these results, the battery-using energy system scenario is compared in terms of environmental performance with an alternative scenario without battery use in order to determine the contribution of energy storage within the whole energy system (case study 3). ... mehrUnder the given modelling assumptions, the use of battery storage results in increased environmental impacts in the majority of the assessed categories, both in comparison with pumped hydroelectric storage (case study 1) and in comparison with the standard small-scale energy system without battery storage (case study 3). Regarding heat storage, the underlying case study shows a low relevance of environmental impacts within the energy system.