Case studies·Oakwood Village, Toronto

Project snapshotDuplexService upgrade

A new duplex on one 200 A service
two meters, two panels

A full rebuild into an owner's home and a basement suite. We calculated both units by the Code's duplex method, fit them on a single 200 A service with a meter and panel for each, and wired the house from the studs out.

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Basement suite with a ductless mini-split heat pump and its own electrical panel, new duplex in Oakwood Village, Toronto — The suite: its own panel and heat pump

176 A

Calculated load, both units

200 A

One service, two meters

60+

Pot lights, fire-rated in the suite

ESA Certificates of Acceptance

1The challenge

A house rebuilt to the studs by a custom builder, as an owner's home upstairs and a one-bedroom suite below. Each unit needed its own meter and panel. The suite is heated electrically, with four zones of radiant floor and a mini-split, and both units have electric ranges, dryers and water heaters. Added up unit by unit, the panels come to more than 200 A, so the question was whether one 200 A service would do or the house needed something larger.

2What we did

Load calculation for each unit by the Ontario Electrical Safety Code: about 109 A for the upper unit and 104 A for the suite, then combined by the duplex method at 100% of the larger plus 65% of the smaller, for 176 A
Toronto Hydro service upgrade to 200 A, with a dual meter centre, mast and weatherhead, coordinated before the stucco went on
A 200 A, 42-circuit panel for the owner and the shared mechanicals, and a 125 A, 32-circuit panel for the suite, so the suite has its own meter and its own bill
Rough-in timed to the framing: 60+ pot lights, 70+ receptacles and 25+ dedicated circuits, including four-zone radiant floor heat and a mini-split in the suite
An electrification roadmap while the walls were open, with an EV conduit and reserved breaker space so a charger can go in later without opening walls
Radiant floor commissioned with a thermal camera, confirming all four zones heat evenly before the suite was handed over
ESA rough-in, floor heating and final inspections, with a Certificate of Acceptance for each unit

3The result

Two independent homes on one 200 A service, calculated at 176 A with room to spare. Each unit has its own meter and panel, both were accepted by ESA, and the house is ready for an EV charger when the owners want one.

The service calculation

Two units, one service, by the Code's duplex method

Each unit is calculated on its own, then the Code combines them, because two households rarely peak at the same time.

Upper unit, owner's homeCalculated on its own

109 A

Lower unit, basement suiteElectric radiant floor heat

104 A

Both added straight togetherWould suggest a larger service

213 A

Combined by the duplex method100% of the larger plus 65% of the smaller

176 A

The service200 A at 240 V

200 A

Calculated, not guessed. Adding the two panels together would have pointed to a bigger, costlier service. The Code's duplex method shows one 200 A service carries both units with about 24 A to spare.

Watch the install

From the studs out

On site

A new duplex on one 200 A service

A new duplex on one 200 A service, photo 3

A new duplex on one 200 A service, photo 4

A new duplex on one 200 A service, photo 5

A new duplex on one 200 A service, photo 6

A new duplex on one 200 A service, photo 7

A new duplex on one 200 A service, photo 8

Load assessment first

Then the right install

Building or converting to a duplex? Send your drawings and the equipment list. We will run the load calculation for both units, size the service and send a fixed quote within 1 to 2 business days.

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Straight Answers

The kind we would give before you commit a dollar of capital. Tap a question.

Do I need a 400 A service for a duplex in Toronto?

Often not. The Ontario Electrical Safety Code calculates each unit, then takes 100% of the largest and 65% of the next, because households rarely peak together. This duplex, with an electrically heated suite, calculated to 176 A and fits on one 200 A service.

Can a basement suite have its own meter and panel?

Yes. A dual meter centre on one Toronto Hydro service gives each unit its own revenue meter, and each unit gets its own panel. The suite pays its own bill, and the shared mechanicals can be fed from the owner's panel.

What should I rough in while the walls are open?

Anything that would mean opening finished walls later: conduit and breaker space for an EV charger, a path for solar, heavier wire to the furnace for a future heat pump, and network cabling. It costs a fraction of a retrofit.

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