With sufficient electricity storage capacity, any power production profile may be mapped onto any desired supply profile. We present a framework to determine the required storage power as a function of time for any power production profile, supply profile, and targeted system efficiency, given the loss characteristics of the storage system. We apply the framework to the electrochemical storage of intermittent renewable power, employing a simplifying linear response approximation that permits the entire efficiency behavior of the system to be described by a single scalar figure of merit—the discharge power capacity. We consider three exemplary grid supply scenarios: constant, grid-minus-baseload, and square wave; and two different production scenarios: wind with a capacity factor 32.5%, and solar photovoltaic (PV) with a capacity factor of 14%. For each of these six combinations of scenarios, the storage energy and discharge power capacity requirements are found for a range of system efficiencies. Significantly diminishing efficiency returns are found on increasing the discharge power capacity. Solid-electrode batteries are shown to have two orders of magnitude too little energy to power ratio to be well suited to the storage of intermittent renewable power.