What is an energy storage system (ESS)?

An ESS is one or more components assembled together capable of storing energy for use at a future time. It can include (but is not limited to) batteries, capacitors, and kinetic energy devices (e.g., flywheels and compressed air). Several of these systems can have AC or DC output for utilization.

How many volts can a dwelling unit energy storage system handle?

For dwelling units, an ESS cannot exceed 100 volts between conductors or to ground. An exception dictates that where live parts are not accessible during routine ESS maintenance, voltage exceeding 100 volts is permitted at the dwelling unit energy storage system. This information can be found at 706.30 (A).

What are battery storage power stations?

Battery storage power stations are usually composed of batteries, power conversion systems (inverters), control systems and monitoring equipment. There are a variety of battery types used, including lithium-ion, lead-acid, flow cell batteries, and others, depending on factors such as energy density, cycle life, and cost.

What is a battery ESS & how does it work?

Most of the largest ESSs in the United States use the electric power grid as their charging source. An increasing number of battery ESSs are paired or co-located with a renewable energy facility, which in some cases may be used directly as a charging source.

Are energy storage systems connected to other energy sources?

Energy storage systems can be (and typically are) connected to other energy sources, such as the local utility distribution system. There may be one or more sources connected to an ESS. The connection to other energy sources is required to comply with the requirements of 705.12.

What is an energy storage system?

An energy storage system consisting of batteries installed at a single-family dwelling inside a garage. Article 706 is primarily the result of the work developed by a 79-member Direct Current (DC) Task Group formed by the NEC Correlating Committee.