Electric vehicle energy management systems • Code File, January 2018

Nansy Hanna
February 13, 2018
February 13, 2018 – With the steady increase of electric vehicles on our roads, the 2018 CE Code (publishing this month) includes new Rules that recognize EV energy management systems (EVEMS), which address evolving EV technology and issues associated with future loading on electrical infrastructure.

The proposal to have this in the code was initiated by the Vancouver Electric Vehicle Association, primarily to “address new technology” and “correlate with product standard requirements”. But with similar green initiatives from different levels of governments across the nation, it was imperative to recognize technologies that will control additional EV loads.

The following two definitions were added to Section 8, and changes were made throughout that Section to recognize EVEMS:

Control of electric vehicle supply equipment loads: the process of connecting, disconnecting, increasing, or reducing electric power to [EV] supply equipment loads.

Electric Vehicle Energy Management System:  a means of controlling [EV] supply equipment loads comprised of any of the following: a monitor(s), communications equipment, a controller(s), a timer(s) and other applicable device(s).

Although the last CE Code did not prevent the installation of EVEMS, nor their utilization in determining the overall demand load, the 2018 Rules provide some important clarifications.

The current code considers EVSE (electric vehicle supply equipment) installed in homes and apartment buildings at a demand of 100%. It does not recognize nor specify demand factors for EV loads other than on homes and buildings (e.g. schools, hospitals, hotels, etc.).

An EVEMS is intended to limit the loads in an electrical installation by:
• sharing power between loads,
• switching loads On/Off,
• throttling loads to within given limits,
• controlling loads dynamically in response to external signals from a utility or other power source (e.g. solar panels), or
• controlling loads dynamically and instantaneously in response to monitors of other uncontrolled loads in the electrical installation (load following).

Such control may be exercised at the branch circuit or feeder levels to EVSE.

Recognizing EVEMS in the CE Code will have a positive impact on all involved stakeholders. In fact, significant cost savings are anticipated for both the building industry and utilities by permitting EVEMS in relation to electrical service sizes, feeders or branch circuits. EVSE installed and controlled by energy management systems is capable of summing static and variable loads, and controlling the variable loads such that the aggregate load cannot exceed the circuit or feeder rating. Such designs will shed loads at the level of the building and help reduce peak loads and brownouts.

The cost of increasing infrastructure capacity can be prohibitive, so recognizing load shedding and resource- sharing for EVs in smart homes is critical for accommodating this new technology. Smart energy management system controls are now capable of monitoring and controlling usage, and are able to communicate with SAE J1772-style EVSE for shedding demand peaks.

(In Ontario, EV energy management systems will be accepted prior to the enforcement of the next edition of the Ontario Electrical Safety Code to support 2017 amendments of Ontario Building Code.)

The cost benefits of this technology are significant when it comes to installation as well as through avoiding operational demand load charges. Established technology may also be applied at the feeder or supply level (smart panels) to limit loads.

Nansy Hanna is the director for Engineering & Program Development at Electrical Safety Authority (ESA) where, among other things, she is responsible for product safety, code development, improving harmonization and
alternative compliance, worker safety, and aging infrastructure programs. She is a LEED-Accredited Professional and a member of CSA CE Code-Part I, Sections 24, 32, 46, 50 and 64. Nansy can be reached at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

This article originally appeared in the January 2018 issue of Electrical Business Magazine.

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