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“EV-ready” homes and the impact on residential service • Code File, March 2018

April 4, 2018 | By Nansy Hanna

April 4, 2018 — Continuing our discussion regarding electric vehicle supply equipment (EVSE a.k.a. EV chargers), let’s look at a few examples to understand the load impact on the service size for a typical house, and how changes in the 2018 CE Code facilitate such installations.

Single-dwelling house, 232 m2

• 232 m2 plus 116 m2 basement
• Total living area is 321 m2 (100% of ground and upper floor[s] plus 75% of basement, as per Rule 8-110)
• AC/heat (20A @ 240V) @ 100% = 4800W
• Level 2 EV charger (50A-plug @ 240V) 32A @ 100% = 7700W

Based on the above example and CE Code Rule 8-200(1), the minimum-required service size for this house is 125A with the EVSE installed. Without it, the service size would only need to be 100A.


That said, a 100A service may still be acceptable were an Electric Vehicle Energy Management System to be deployed (as permitted by Rule 8-500), because the EVEMS adjusts the draw of the charging current based on available capacity on the service.

When EVSE is added to an existing house—based on provisions in Rule 8-106—it is permitted to use a detailed (demonstrated) load as obtained from the local distribution company (LDC), which indicates the existing peak demand over the last 12 months plus the nameplate rating of the charger to calculate the new demand.

A utility bill along with information from the supply authority for an existing 279-m2 (3000-sf) house with a 100A service (including A/C, hot tub and electric stove) revealed the peak amperage is around 30A, so the new peak demand is: 30A + 32A = 62A. Although the Rules of Section 8 need to be followed for new houses, this case study reveals there may be sufficient capacity on a typical house service.

Townhome, 111 m2

• 111 m2 plus 46 m2 basement
• Total living is 147 m2
• AC/heat (20A @ 240V) @ 100% = 4800W
• Level 2 EV charger (50A-plug @ 240V) 32A @ 100% = 7700W

Service supply, 6-unit townhomes of 111 m2 (with and without A/C)

When calculating the minimum ampacity of the feeder, calculate the feeder/service based on Rule 8-202(3)(a). Assume the base load is calculated by % and the A/C is considered 100% load. Based on 8-202(3), EV loads are not required to be included as 100%, similar to A/C load, but are permitted to be included in the base calculation with demand factors applied.

The minimum ampacity for the service conductors for these six units shall be based on a 415.2A load.

Similarly, when EVEMS are employed as per the 2018 CE Code, the supply service size for the six units’ townhomes could be reduced. Information on the EVEMS used will be required at the design stage to determine whether a reduction of the service size is permitted.

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 nansy.hanna@electricalsafety.on.ca.

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

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