Comment by kibwen

The article goes into this:

"The old coal generator provided three key values to Oahu, Keefe explained: energy (the bulk volume of electricity), capacity (the instantaneous delivery of power on command), and grid services (stabilizing functions for the grid, wonky but vital to keeping the lights on). The battery directly replaces the latter two: It matches the coal plant’s maximum power output (or “nameplate capacity,” in industry parlance), and it is programmed to deliver the necessary grid services that keep the grid operating in the right parameters."