Battery energy storage units provide an added degree of freedom to a microgrid that allows time-shifting between the generation and use of energy. Microgrid energy storage elements are very similar to any other inverter-based source with the exception of bi-directional power flow capabilities. Having the ability to generate and accept power means that the demand and the supply can be disparate by as far as the power capabilities of the energy storage unit allow. This enables combined heat power systems to support a heat load demand independent of local electric power demand. Having an energy storage element on standby also allows for a certain amount of immediately available power to reduce the need for idling or lightly loaded rotating generators under the n-1 stability criterion. The relative speed of any inverter based source allows a sub-cycle change in power output to ensure that dynamic loads will be supplied regardless of the slow reaction of larger rotating sources that require seconds of response time to transients.
Thirdly, they can act as a UPS system during grid faults, providing backup power for some time even for non-essential loads while the microgrid is islanded. Lastly, the energy storage element can provide an economic and/or logistical advantage by regulating the power drawn by and supplied to the grid interface. This not only permits capitalizing on fluctuating power prices, but even regulating a line loading by making better use of off-peak hours to supply the daily energy needs.