A site rarely consumes at a steady rate: peaks in the morning, a dip at night, spikes when a machine starts up. Contracted power is sized for the peak, and the rest of the time it goes unused. A storage battery smooths that curve: it charges when energy is available or inexpensive, and releases it at peak time.
The second benefit is continuity. During an outage of a few minutes, the battery takes over and leaves time to shut down an operation cleanly or start up another source. For a cold store, a control room or a production line, those minutes are worth the hire.
Sizing is based on your actual data, never on an estimate: it is the first thing we ask you for.