This study determines the lifetime cost of 9 electricity storage technologies in 12 power system applications from 2015 to 2050. We find that lithium-ion batteries are most cost effective beyond 2030, apart from in long discharge applications. The performance advantages of alternative technologies do not outweigh the pace of lithium-ion cost reductions. Thus, investments in alternatives might be futile, unless performance improvements retain competitiveness with lithium ion. These insights increase transparency around the economic viability of electricity storage and can help guide research, policy, and investment activities to ensure cost-efficient deployment. HIGHLIGHTSLifetime cost for 9 storage technologies in 12 applications from 2015 to 2050 Lowest lifetime costs fall by 36% (2030) and 53% (2050) across the 12 applications Lithium-ion batteries are most competitive in majority of applications from 2030 Pumped hydro, compressed air, and hydrogen are best for long discharge applications Schmidt et al., Joule 3, 81-100 January 16, SUMMARYThe future role of stationary electricity storage is perceived as highly uncertain. One reason is that most studies into the future cost of storage technologies focus on investment cost. An appropriate cost assessment must be based on the application-specific lifetime cost of storing electricity. We determine the levelized cost of storage (LCOS) for 9 technologies in 12 power system applications from 2015 to 2050 based on projected investment cost reductions and current performance parameters. We find that LCOS will reduce by one-third to one-half by 2030 and 2050, respectively, across the modeled applications, with lithium ion likely to become most cost efficient for nearly all stationary applications from 2030. Investments in alternative technologies may prove futile unless significant performance improvements can retain competitiveness with lithium ion. These insights increase transparency around the future competitiveness of electricity storage technologies and can help guide research, policy, and investment activities to ensure cost-efficient deployment.