This paper presents a detailed analysis of the levelized cost of storage (LCOS) for different electricity storage technologies. Costs were analyzed for a long-term storage system (100MW power and 70GWh capacity) and a short-term storage system (100MW power and 400MWh capacity). Detailed data sets for the latest costs of four technology groups are provided in this paper. The LCOS method allows a cost comparison of technologies in different system designs and various operation modes. The results for the long-term storage show that Pumped-Storage Hydroelectricity has the lowest LCOS among the mature technologies today. Power to Gas technologies, once established on the market, may also provide long-term electricity storage at even lower LCOS. Pumped-Storage Hydroelectricity is also the cheapest technology for short-term storage systems. Battery systems at the moment still have high costs but are expected to have a sharp price decrease in the near future. Power to Gas and adiabatic Compressed Air Energy Storage systems may become cost competitive as short-term storage systems as well. The detailed analysis of the cost components shows that the cost composition is very inhomogeneous among the technologies. Plant design optimized to the application is therefore crucial for cost minimization. Sensitivity analysis shows that for most technologies the amount of energy discharged as well as the cost of electricity purchase are the most influential factors for the LCOS.