What gauge wire do I need for different electrical circuits in my New Brunswick home?

Using the correct wire gauge for each circuit in your home is fundamental to electrical safety — undersized wire overheats, creating a fire hazard, while oversized wire wastes money unnecessarily. The Canadian Electrical Code (CEC) specifies minimum wire sizes based on circuit amperage, and TSANB inspectors verify compliance during inspections.

Wire Gauge Basics

Electrical wire in Canadian homes is measured in AWG (American Wire Gauge). The numbering is counterintuitive: smaller numbers mean thicker wire. Thicker wire carries more current safely because it has lower resistance and generates less heat.

Residential wiring in New Brunswick uses NMD90 cable (non-metallic dry, rated for 90°C) — commonly known by the brand name "Romex" (though Romex is technically a US brand; Canadian equivalents are made by Southwire, Nexans, and others). NMD90 cable contains two or three insulated conductors plus a bare ground wire, all inside a plastic sheath.

Wire Gauge by Circuit Type

| Circuit Type | Breaker Size | Wire Gauge | Cable Type | Common Use |
|-------------|-------------|-----------|------------|------------|
| General lighting | 15 amp | 14 AWG | 14/2 NMD90 | Bedroom, hallway, closet lights |
| General outlets | 15 amp | 14 AWG | 14/2 NMD90 | Bedroom, living room outlets |
| Kitchen countertop | 20 amp | 12 AWG | 12/2 NMD90 | Small appliance circuits (CEC minimum 2 per kitchen) |
| Bathroom outlet | 20 amp | 12 AWG | 12/2 NMD90 | Bathroom GFCI receptacle |
| Laundry outlet | 20 amp | 12 AWG | 12/2 NMD90 | Washing machine outlet |
| Garage/workshop outlet | 20 amp | 12 AWG | 12/2 NMD90 | Power tool circuits |
| Outdoor outlet | 20 amp | 12 AWG | 12/2 NMD90 | GFCI-protected exterior receptacles |
| Dishwasher | 15 or 20 amp | 14 or 12 AWG | 14/2 or 12/2 | Dedicated dishwasher circuit |
| Microwave (built-in) | 20 amp | 12 AWG | 12/2 NMD90 | Dedicated microwave circuit |
| Refrigerator | 15 amp | 14 AWG | 14/2 NMD90 | Dedicated fridge circuit |
| Electric range/oven | 40 amp | 8 AWG | 8/3 NMD90 | 240V range circuit |
| Electric dryer | 30 amp | 10 AWG | 10/3 NMD90 | 240V dryer circuit |
| Electric water heater | 30 amp | 10 AWG | 10/2 NMD90 | 240V water heater |
| Baseboard heater (1500W) | 15 amp | 14 AWG | 14/2 NMD90 | 240V baseboard heat |
| Baseboard heater (2000W) | 20 amp | 12 AWG | 12/2 NMD90 | 240V baseboard heat |
| Central AC / Heat pump | 20–40 amp | 10–8 AWG | Varies | Dedicated 240V circuit |
| EV charger (Level 2) | 40 amp | 8 AWG | 8/2 NMD90 | Dedicated 240V, 40A circuit |
| EV charger (high power) | 50 amp | 6 AWG | 6/2 NMD90 | Dedicated 240V, 50A circuit |
| Hot tub | 40–50 amp | 8–6 AWG | 8/2 or 6/2 | Dedicated 240V with GFCI |
| Sub-panel feeder (60A) | 60 amp | 6 AWG | 6/3 NMD90 | Garage or workshop sub-panel |
| Sub-panel feeder (100A) | 100 amp | 3 AWG | 3/3 NMD90 | Large workshop or secondary suite |

Key CEC Rules for Wire Sizing

Never upsize a breaker without upsizing the wire. A 15-amp breaker protects 14-gauge wire. If you swap in a 20-amp breaker without replacing the wire with 12-gauge, the breaker won't trip until the wire is already dangerously overheated. This is one of the most dangerous code violations found in NB homes.

You CAN use heavier wire on a smaller breaker. Running 12-gauge wire on a 15-amp circuit is perfectly acceptable (and some electricians prefer it for future flexibility). You just can't do the reverse.

Continuous loads at 125%. The CEC requires that circuits serving continuous loads (loads that run for 3+ hours — like baseboard heaters, EV chargers, and some lighting) be rated at 125% of the load. Example: a 1,920W baseboard heater on 240V draws 8 amps, but 8 × 1.25 = 10 amps, so a 15-amp circuit with 14-gauge wire is technically adequate. However, for 2,000W heaters (8.33A × 1.25 = 10.4A), a 15-amp circuit is still sufficient but leaves less margin.

Voltage drop on long runs. For wire runs exceeding 15 metres (50 feet), voltage drop becomes a concern. The CEC recommends no more than 5% total voltage drop from the panel to the outlet. For long runs (basement to detached garage, for example), upsizing the wire by one gauge compensates. Example: a 40-foot run that would normally use 14-gauge should use 12-gauge if it extends to 80+ feet.

NB-Specific Considerations

Baseboard heating circuits: New Brunswick's heavy reliance on electric baseboard heat means many homes have 5–10 heating circuits. Each baseboard heater gets either a dedicated circuit or shares with one adjacent heater. The CEC treats heating as a continuous load (125% rule applies), so wire sizing is critical.

Common NB baseboard wiring:

• 750W heater: 3.13A at 240V → 14 AWG on 15A breaker (adequate)


• 1,000W heater: 4.17A at 240V → 14 AWG on 15A breaker (adequate)


• 1,500W heater: 6.25A at 240V → 14 AWG on 15A breaker (adequate)


• 2,000W heater: 8.33A at 240V → 12 AWG on 20A breaker (recommended)


• Two 1,500W heaters on one circuit: 12.5A at 240V → 12 AWG on 20A breaker (required)

Well pump circuits: Many rural NB homes use well pumps. A standard 1/2 HP submersible well pump needs a dedicated 15-amp circuit with 14-gauge wire. A 1 HP pump needs a 20-amp circuit with 12-gauge wire. Because well pumps are motor loads with high starting current, the circuit must handle startup surge of 2–3 times running amps — the breaker accommodates this with its trip delay, but the wire must still be properly sized for the continuous running load.

Underground runs: Wire running underground to a detached garage, shed, or outbuilding must be either:

• NMWU cable (rated for wet/underground use) direct-buried at CEC-specified depth, OR


• Standard NMD90 pulled through PVC conduit buried at specified depth

The wire gauge must account for voltage drop over the underground distance.

Wire Costs in New Brunswick (2026 Approximate)

| Wire | Per Metre | Per 75m Roll |
|------|----------|-------------|
| 14/2 NMD90 | $1.00–$1.50 | $75–$110 |
| 12/2 NMD90 | $1.50–$2.00 | $110–$150 |
| 10/2 NMD90 | $2.50–$3.50 | $190–$260 |
| 10/3 NMD90 | $3.50–$5.00 | $260–$375 |
| 8/3 NMD90 | $5.00–$7.00 | $375–$525 |
| 6/3 NMD90 | $7.00–$10.00 | $525–$750 |

Prices at Kent Building Supplies, Home Hardware, and electrical supply houses in Moncton, Fredericton, and Saint John. Prices fluctuate with copper market conditions.

Common Mistakes Found in NB Homes

• 14-gauge wire on 20-amp breakers: Found in older homes where a homeowner upgraded the breaker without upgrading the wire. Extremely dangerous.
• Extension cord as permanent wiring: Running a cord through a wall or ceiling to permanently supply power. Violates CEC and is a fire hazard.
• Mixed gauge on one circuit: Starting with 12-gauge from the panel but splicing to 14-gauge partway through. The 20-amp breaker won't protect the 14-gauge section.
• Wrong cable type underground: Using standard NMD90 buried directly in soil (it's not rated for direct burial — the sheath degrades).

All new wiring and circuit modifications in New Brunswick require a TSANB permit and inspection to verify proper wire gauge, connections, and code compliance.

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