The electrical system in a custom home is one of the most complex — and most expensive to change after the fact. Decisions made during the design and rough-in phases determine what your home can do for the next 30 years. Moving a panel after drywall is hung costs ten times what it costs during framing. Running smart home wiring after insulation is in place means tearing open walls. Getting the electrical plan right at the beginning is not optional — it is essential.
Whether you are a homeowner managing your own custom build or a general contractor coordinating trades, this guide covers the critical electrical decisions that need to happen before the first wire is pulled.
Panel sizing: plan for the future
Most new custom homes in Ontario should be built with a 200-amp service at minimum. For homes over 3,000 square feet, or homes with electric vehicle chargers, hot tubs, heated driveways, or multiple HVAC zones, a 400-amp service or a 200-amp service with a subpanel strategy is worth serious consideration. The cost difference between a 200-amp and 400-amp service during new construction is a fraction of what a future upgrade would cost.
Work with your electrician to perform a load calculation based on the full list of appliances and systems planned for the home. Ontario Electrical Safety Code (OESC) Rule 8-200 governs service and feeder calculations, and your electrician should walk you through the math so you understand exactly how much capacity you are building in.
Rough-in: the most critical phase
Rough-in is when all wiring, boxes, and conduit are installed before insulation and drywall. This is your one opportunity to get everything in the walls affordably. Every outlet location, every switch, every dedicated circuit, every low-voltage run for speakers, cameras, networking, and smart home systems needs to be planned and installed during this phase.
- Outlet placement: walk every room with the floor plan and furniture layout in hand
- Kitchen circuits: minimum two 20A small appliance circuits plus dedicated circuits for range, dishwasher, microwave, and fridge
- Bathroom circuits: dedicated 20A GFCI-protected circuits for each bathroom
- Garage: 240V/50A circuit roughed in for future EV charger, even if not needed today
- Home office: dedicated 20A circuits separate from general lighting circuits
- Outdoor: weatherproof outlets on every face of the house, landscape lighting conduit runs
Smart home wiring and low-voltage planning
Smart home technology changes fast, but the physical infrastructure — the wiring in your walls — does not. Run Cat6a ethernet cable to every room, even if you plan to use Wi-Fi. Install a structured wiring panel (media closet) with adequate power and ventilation. Pre-wire for security cameras at corners and entry points. Run speaker wire if you want distributed audio. All of this costs very little during rough-in and is extremely expensive to retrofit.
For lighting control, consider a centralized smart lighting system during new construction. Systems like Lutron RadioRA or Caseta, or hardwired home automation panels, are far more reliable than aftermarket smart switches and can be programmed to create scenes, schedules, and automated responses.
The golden rule of custom home electrical: if there is even a 30% chance you might want something in the future, run the wire now. Empty conduit and capped junction boxes cost almost nothing during construction and save thousands later.
ESA inspections for new construction
New construction in Ontario requires multiple ESA inspections. The rough-in inspection happens after all wiring is installed but before insulation and drywall go up — this is when the inspector verifies wire routing, box placement, grounding, and code compliance. A final inspection happens after the home is complete and all devices are installed. Both must pass before occupancy.
Safer Electric works with custom home builders across the GTA. We attend design meetings, coordinate with other trades during rough-in, and manage the full ESA inspection process. Call us during the planning phase — not after framing starts.
Safer Electric Team
Licensed Electricians · Toronto, ON
Our team of licensed GTA electricians writes these guides to help homeowners make informed decisions. Every article is reviewed for technical accuracy.