Home Energy Storage Systems – Code File, February 2022

February 24, 2022 – As we continue to move towards net zero, the need for energy storage systems (ESS) will continue to increase in residential and non-residential applications. Unfortunately, some confusion has arisen around the 2021 Canadian Electrical Code requirements for residential applications, so let’s look at installing an ESS in a dwelling.

The CE code introduced two definitions for energy storage systems: residential use and non-residential use. The first is marked as being suitable for residential use and meets the requirements of ANSI/CAN/UL 9540 “Energy Storage Systems and Equipment”.

Additionally, a note in Appendix B of Rule 64-918(1) specifies that UL 9540 requires ESSs intended for dwellings to be marked “Suitable for use in residential dwellings where permitted”. (Non-residential systems are defined as unmarked as suitable for residential use.)

These definitions introduce a restriction which appears to be based on UL 9540, but such a restriction is not actually provided for by the standard. In addition, to date, there are no energy storage systems on the market bearing the statement “Suitable for use in residential dwellings where permitted”.

In fact, the purpose of the UL 9540 marking of EHS with “Suitable for use […]is to allow units who have passed additional rigorous testing to be installed in the living or habitable spaces of a housing unit (when authorized by the AHJ).

Rule 64-918(1) further prohibits the installation of ESSs with a storage capacity greater than 1 kWh or using lithium-ion batteries in dwellings. Period.

In the meantime, the UL 9540 standard allows certified ESSs that are not marked for residential use, but meet the standard’s regular testing, to be installed in non-habitable or non-habitable spaces of a dwelling unit. (e.g. utility closets, attached garages or storage spaces). This is evident in Table E.1 “ESS for residential use” where it is further clarified by indicating the capacity and separation requirements of permitted ESS in dwellings.

This restriction in the CE code also conflicts with NFPA 855 “Installation of Stationary Energy Storage Systems”. Clause 15.6.1 allows installation of ESS in attached and detached garages; in closed utility closets and storage spaces.

NFPA 855 further specifies that when the room or space where the ESS is to be installed is unfinished, the walls and ceiling must be protected with at least 5/8 in. Type X gypsum board. (Note: NFPA 855 requires ESS to comply with UL 9540).

Section 64-918(2), which prohibits the installation of ESS using batteries below grade, also raises questions as it is unclear whether this applies to dwellings. If an AHJ is considering allowing ESS in housing, should they be allowed in basements? In a typical home, a laundry room in a basement – or an unfinished basement – is not a habitable area.

Therefore, a basement could be a good location for an ESS. (Although other factors should be taken into consideration, e.g. is the basement in a flood prone area, is there a working smoke detector, will there be it a dedicated EHS storage room with a fire rating of at least 1 hour per the intent of NFPA 855).

Section 64-918(6) permits the installation of “residential use” ESSs in garages of dwelling units, provided that a single ESS does not exceed 20 kWh of storage capacity; several ESSs do not exceed 40 kWh in capacity; and ESSs are spaced at least 1 m apart.

Knowing that the intention of UL 9540 to mark EHS with “Suitable for use […]is to permit such units in habitable or habitable areas of dwelling units, one wonders if subrule 64-918(6) really intends to permit the installation of ESS (approved according to UL 9540) in the garage of a dwelling unit. This approach would be consistent with NFPA 855.

It is important to review and understand the intent of these new rules and consult with your AHJ during the design phase for projects involving installations of energy storage systems in homes.

In the meantime, the Section 64 Technical Sub-Committee is working on a proposal to update the EHS rules, with specific guidance for residential applications. To visit CSA Group Public Review Page and get involved.


Nansy Hanna, P.Eng., is Senior Manager, Engineering and Regulatory, at the Electrical Safety Authority of Ontario (ESA). She is also Chair of the Canadian Advisory Council on Electrical Safety (CACES) and a member of the ULC Advisory Council, the CSA Technical Committee on Industrial, Consumer and Commercial Products and CE Code Part I of the CSA, sections 24, 32 and 46. She can be reached at [email protected].

This column, along with other great content, appears in the February 2022 edition of Electrical Business Magazine. Back issues can be found in our digital archive.

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