Think of a sinusoidal demand for energy, with a period of a few tens of seconds. By charging when demand is low and discharging when demand is high, peak load is lowered.

Sounds like a logical extension to power factor correction. Large consumers have long been installing capacitors to compensate for inductive loads. Although this new tech is over a longer time frame.

To put this in context for others, although domestic customers are normally only billed for real power this is not the case for industrial consumers. Reactive power is significant as they are billed not just for energy used but also for peak power drawn.