Code Compliant Connection of Portable and Movable Battery Energy Storage Systems
This document addresses code compliant connection and use of portable/movable BESS that are certified to the appropriate safety standards and which comply with the governing building and electrical codes.
Portable and movable Battery Energy Storage Systems (BESS) have rapidly evolved in recent years, making it difficult for consumers, contractors, and Authorities Having Jurisdiction (AHJs) to understand how this equipment fits within the existing landscape of products, codes, and standards. As with any other energy storage system, portable/movable BESS units have safety concerns for people and property related to design, manufacture, installation, and operation. Unfortunately, many portable/movable BESS do not undergo the same certification, permitting, and inspection processes as permanent installations, which can result in unsafe installations.
This document addresses only portable/movable BESS that are certified to the appropriate safety standards needed for product certification (see definitions and appendix below), and comply with the governing building and electrical codes. The local governing body must be contacted to determine required permits, plans, and licensing required for installation. These BESS units are intended to temporarily power premises wiring, either independently of the electrical grid, or in conjunction with the electrical grid when properly certified and configured. These units may either be capable of being lifted and carried by an individual, have wheels that provide for mobility, or be installed on a cart or trailer that can be moved by hand or towed by a vehicle.
This document is intended as guidance for users, installers, contractors, homeowners, and AHJs. An AHJ is the organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure. An AHJ may be your local building department or fire department.
The scope of this document is limited to the safe installation, configuration, use, storage, and transportation of certified (listed) devices. This document assumes all systems use certified (listed) components that are installed by qualified persons in compliance with manufacturer’s instructions and listings, and be properly permitted and inspected per local code requirements. It is advisable to check with your local officials for a determination of licensing, permitting, and insurance requirements. The term “installed” refers to the portions of the system that are permanent, and may include a power inlet, transfer switch, or energy management component along with the necessary wires and cables which allow the portable/movable energy storage device to be temporarily connected to the premises wiring. Portable and movable BESS are not intended to be permanently installed.
The consequences of not following the applicable regulations and requirements could potentially result in fires, loss of insurance coverage, or liability issues for the installer.
Some units are advertised as being able to be plugged into a regular receptacle to provide power to the premises wiring. These units are not addressed here, and may instead be addressed in a future document as they may not be suitable for use in most U.S. installations at this time. The information provided here is intended for informational purposes only and is offered in good faith. It is the responsibility of a qualified person with the skills and knowledge to ensure full compliance with local codes and standards.
We will address proper design and common installations of portable and movable energy storage systems to understand safe operation when temporarily connected to a building’s permanent wiring (premises wiring).
Although not all possible configurations are included, we have addressed the most common portable ESS configurations and applications at the time of publication. This document contains information that may appear complex to some readers less experienced with this technology, but the intent is to make the document accessible and helpful to a diverse audience from engineers, to installers, code officials, and end users. In order to make the document usable and informative, there are both technical language explanations and plain English explanations of the information.
This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Solar Energy and Technologies Office Award Number DE-EE0009001.0000. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.
