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Design and Installation of Electrical Energy Storage Systems - Code Compliance Brief

The intent of this brief is to provide information about Electrical Energy Storage Systems (EESS) to help ensure that what is proposed regarding the EES ‘product’ itself as well as its installation will be accepted as being in compliance with safety-related codes and standards for residential construction.  Providing consistent information to document compliance with codes and standards to all relevant parties responsible for verifying compliance with those codes and standards (e.g., code officials, builders, contractors, designers, utilities, fire officials, etc.) is expected to result in increased compliance and more timely, less challenging and more uniform plan review and field inspections.

An increased number of electrical energy storage systems (EESS) utilizing stationary storage batteries are appearing on the market to help meet the energy needs of society—most notably storage of power generated from renewable resources or the electric grid for use during power outages or peak electrical demand periods.  Currently, these systems are not required by codes covering residential construction, but when used, the EES itself and its installation must be safe and remain safe.  Although the 2015 International Fire Code (IFC) does address some of these systems, the 2015 International Residential Code (IRC) does not specifically address the design and installation of these systems for residential construction.

One requirement for homes to qualify as a U.S. Department of Energy Zero Energy Ready Home (DOE Solar Energy Ready Program Requirements,, it must be constructed, at a minimum, as “solar energy ready.” and likely require installation of a system to store excess energy for subsequent use. Some builders and homeowners choose to install an energy storage system—whether they are participating in a program or not—simply to have backup power during power outages. This brief provides further clarification and resources to assist with designing, constructing, installing, and commissioning these energy storage systems and/or system components and verifying that they are safe. The intent of solar energy ready requirements is to provide a penetration free and shade free portion of the roof, called the solar zone. This helps ensure future installation of a solar energy system is not precluded by the original design and layout of the building and its associated equipment.

The following sections list the applicable code and standard requirements and details helpful for Plan Review. The Field Inspection section then provides details for inspecting “…electrical energy storage systems utilizing stationary storage batteries.” For resources on technical validation, best practices, and measure guidelines, refer to the Technical Validation/Reference Materials section of this brief.

The lists and provisions provided below in each section are intended to target the main code sections and provisions. There may be other references, code sections, standards, testing methods, etc., that affect the technology or other assemblies or functions of the building. 

Plan Review

This section provides details in the 2015 International Residential Code (IRC) and International Energy Conservation Code (IECC), and the language (underscored and struck-through) from code change proposals being considered for the 2018 IRC.  The language underscored and struck-through could change during the final code hearings that occur in late October 2016.  (Go to for additional information on the code proposals and hearings.)  This Code Compliance Brief will be updated accordingly after the hearings and final online Governmental Consensus voting period in November 2016.

2015 IRC, Section R104 Duties and Powers of the Building Official

2015 IECC/IRC, Section R104.1 General.  The building official has authority to render interpretations of this code and to adopt policies and procedures in order to clarify the application of its provisions.  Such interpretations, policies and procedures shall be in conformance with the intent and purpose of this code. 

R102.1/R104.11 Alternative Materials, Design and Method of Construction and Equipment.  The provisions of this code are not intended to prevent the installation of any material or prohibit any design or method of construction not specifically prescribed in the 2015 IECC/IRC, provided that any such alternative has been approved.  The building official is permitted to approve an alternative material, design, or method of construction where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and the material, method, or work offered is for the purpose intended, not less than the equivalent of that prescribed in the code.  Compliance with the specific performance-based provisions of the International is an alternative to the specific requirements of this code. 

For some EESSs, there is a lack of specific requirements in the codes and standards, however, some are covered in existing and recently approved codes and standards that are available for adoption and application.  This poses a challenge to determining the acceptability and compliance based on specific performance-based provisions as an alternative.

R104.11.1 Tests.  Whenever there is insufficient evidence of compliance with the provisions of this code, or evidence that a material or method does not conform to the requirements of this code, or in order to substantiate claims for alternative materials or methods, the building official has authority to require tests as evidence of compliance to be made at no expense to the jurisdiction.  Test methods shall be as specified in this code or by other recognized test standards.  In the absence of recognized and accepted test methods, the building official shall approve the testing procedures.  Tests shall be performed by an approved agency.  Reports of such tests shall be retained by the building official for the period required for retention of public records. 

Per the 2015 IECC/IRC, Section R103.3/R106.3 Examination of Documents, the code official/building official must examine or cause to be examined construction documents for code compliance.

Construction Documentation.  Review the construction documents for details describing energy storage system and/or components construction techniques.  (Bullet items underscored are based on the 2018 ICC code proposals.)

2015 IECC/IRC, Section R103.2/N1101.5 Information on construction documents.  Construction documents should include:

  • Type of energy storage system, design, size and location
  • System ratings, testing, and labeling
  • Stored energy capacity (kW)
  • Conduit, wiring, and electrical layout design
  • Inverter location and listing
  • Emergency shut-off controls.


Section R201 Definitions

New definition:

Battery System, Stationary Storage.  A rechargeable energy storage system consisting of electrochemical storage batteries, battery chargers, controls, and associated electrical equipment designed to provide electrical power to a building.  The system is typically used to provide standby or emergency power, an uninterruptable power supply, load shedding, load sharing or similar capabilities.

The definition provides the code user with information on battery storage systems, and is identical to a definition being proposed for the IFC and International Building Code (IBC).

The Underwriters Laboratory (UL 9540), “Outline of Investigation for Energy Storage Systems and Equipment,” provides construction and performance requirements for investigating and listing stationary storage battery systems.  This standard evaluates their ability to operate under both normal operating conditions and under certain fault conditions.  In addition, UL 1973, “Batteries for Use in LER and Stationary Applications,” provides construction and performance requirements for batteries used as a component of an EESS.  It is important to note that an EESS can be considered a unitary pre-packaged systems or assemblies of matched components where the entire system can be tested and listed to UL 9540.  Where an EESS is assembled from different “mix/matched” components, each component would have to be listed, and then, the assembly of those components comprising the EESS would be addressed on-site using the IRC as a basis for review and approval.


New text:


R327.1 General.  Stationary storage battery systems, where provided, shall comply with the provisions of this section.

R327.2 Equipment listings.  Stationary storage battery systems shall be listed and labeled for residential use in accordance with UL 9540.


  1.  Where approved, repurposed unlisted battery systems from electric vehicles are allowed to be installed outdoors or in detached sheds located a minimum 5 ft (1524 mm) from exterior walls, property lines and public ways.
  2.  Battery systems that are an integral part of an electric vehicle are allowed provide the installation complies with Section 625.48 of NFPA 70
  3.  Battery systems less than 1 KWh (3.6 Mega joules)


Because ESS is a new, evolving technology, exceptions to R327.2 are provided to allow for installations of repurposed, non-listed ESS from electric vehicles. However a 5-foot separation distance from exterior walls, the property line, and public ways to mitigate the performance of the equipment under fault conditions, which was not determined as part of a listing investigation. Installations using ESSs that are integral to electric vehicles also are allowed, provided they comply with the National Fire Protection Association (NFPA), - NFPA 70  “National Electrical Code” requirements that specifically cover such installations.  A final exception exempts battery systems under 1 KWh, which is slightly greater than two 12-V, 40-AH batteries.  This exemption covers common household standby power systems for tools, alarm systems, and other appliances from compliance with this section. NFPA 70-2017:  National Electrical Code was revised and approved for publication in August 2016, see

R327.3 Installation. Stationary storage battery systems shall be installed in accordance with the manufacturer's instructions and their listing, if applicable, and shall not be installed within the habitable space of a dwelling unit.

R327.4 Electrical installation. Stationary storage battery systems shall be installed in accordance with NFPA 70. Inverters shall be listed and labeled in accordance with UL 1741 or provided as part of the UL 9540 listing. Systems connected to the utility grid shall use inverters listed for utility interaction.

The R327.4 electrical installation requirements are based on R324.3, but include an option for inverters included as part of an EESS that is tested and listed to UL 9540. It also is important to note that NFPA 70-2017 includes a new article 706, “Energy Storage Systems,” that governs ESS installation, disconnection, shutdown, and safety labeling on energy storage systems.  This new article could be used for guidance on EESS safety.  The IRC adopts the National Electrical Code by reference.  The 2018 IRC (currently under development) should reference the revised NFPA 70-2017.

R327.5 Ventilation.  Indoor installations of stationary storage battery systems that include batteries that produce hydrogen or other flammable gases during charging shall be provided with ventilation in accordance with Section M1307.4.

R327.5 includes ventilation requirements that must be provided for indoor installations of EESS technologies, such as those including lead-acid batteries capable of producing hydrogen gas during charging.

R327.6 Protection from impact. Stationary storage battery systems installed in a location subject to vehicle damage shall be protected by approved barriers.

The R327.6 vehicle protection requirements are based on Section M1307.3.1.

Field Inspection

Per the 2015 IECC, Section R104 Inspections, construction or work for which a permit is required is subject to inspection.  Construction or work is to remain accessible and exposed for inspection purposes until approved.  Required inspections include footings and the foundation, framing and rough-in work, plumbing rough-in, mechanical rough-in, and final inspection.

Per the 2015 IRC, Section R109 Inspections, for onsite construction, from time to time the building official, upon notification from the permit holder or his agent, can make or cause to be made any necessary inspections.  Further details are provided for inspections regarding foundation, plumbing, mechanical, gas and electrical, floodplain, frame and masonry, and final inspection.  Any additional inspections are at the discretion of the building official.

This section provides details for inspecting to the specific provisions for design and installation of energy storage systems where one or more specific types of inspection called for by the IECC or IRC may be necessary to confirm compliance.  To confirm code compliance, final inspection typical type of inspection performed.  (Bullet items underscored are based on the 2018 ICC code proposals.)

  • Confirm the type of energy storage system, design, size and location per the approved construction documentation
  • Confirm system ratings, testing and labeling
  • Confirm inverter location and listing
  • Confirm emergency shut off controls location and listing per approved construction documents.
Technical Validation(s)

This section provides additional related information and references to materials that are applicable to the provision.


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