The literature on electrical energy storage (EES) is technical and complex which this paper aims to simplify. It quantifies the current scale, costs and value of different types of EES and compares them to peaking generators and interconnectors. Worldwide, dams have 2,700 times the storage capacity of pumped storage, which accounts for 99% of conventional EES, batteries making up the rest. Indirect use of hydro power, and in future, electric vehicles, adds to their value and if accessible at reasonable cost, would be cheaper than conventional EES. EES, peakers and DC interconnectors can offer flexibility services which considerably enhance their value, but hopes of a battery revolution enabling a smarter electricity system should not be exaggerated.