As the solar industry has expanded, more and more technology has become accessible to customers. One of the biggest requests from customers is storage. Customers want the ability to take advantage of the extra energy that they produce and have the ability to peak shave. With a traditional, behind-the-meter system, any excess energy that the PV system produces that is not used by the facility, is sent back to the utility. The customer is then credited for this excess; this is called net metering.
When the PV system is not producing enough electricity to power the building (for example, on a rainy day or at night), the building will pull energy from the grid, the same way as it would if there were no PV system installed. Larger users of electricity are usually charged for demand or capacity (measured in kilowatts, kW or kilovolt ampere, kVa), as well as being billed for usage or consumption (measured in kilowatt hours, kWh). The utility uses demand meters to measure the peak kW registered in 15 minute intervals. The customer is then billed for the highest peak kW registered during the billing period (Max Demand Charge). Energy storage has the ability to solve both of these problems.
With energy storage, a customer can store any excess energy that they are producing in their battery storage system and then utilize it when they are not producing enough electricity later. This system essentially makes them independent of the grid. Only in severe cases where the building is suddenly using an abnormally high amount of energy and the panels have not produced enough energy, will the customer have to resort to pulling energy from the grid. Similarly, the system would only export power back to the grid when both the energy needs of the building are being met and the battery storage system was completely full.
A battery storage system also has the ability to reduce demand charges through something called peak shaving. When the customer is pulling a large amount of energy from the grid and is potentially racking up large demand charges, the battery storage system can kick in and provide excess power to the building, therefore reducing the amount of energy that must be pulled from the grid. While it is unlikely that a customer will be able to eliminate all demand charges, a peak shaving battery system can greatly reduce them. Large energy users can have thousands of dollars worth of demand charges in a single month, making the investment in a battery storage system well worth the investment. In some states, local regulations set forth by the state require large solar energy systems to also be equipped with a storage solution to qualify for solar incentives.