How to Choose the Right Breaker Size for Your Circuit

A breaker that's too small trips constantly. A breaker that's too large won't trip when it should — which means overheated wires and potential fire. The breaker size must match the wire gauge, and the wire gauge must match the load. Here's the definitive guide.

The Rule Is Simple

The breaker protects the wire, not the appliance. A 15A breaker allows up to 15 amps to flow through 14 AWG wire. If you put a 20A breaker on 14 AWG wire, the breaker won't trip until 20A — but the wire is only rated for 15A. The wire overheats before the breaker acts.

Breaker Size to Wire Gauge Chart

Breaker Size	Minimum Wire Gauge	Common Circuit Type
15A	14 AWG	General lighting, bedrooms, living rooms
20A	12 AWG	Kitchen counters, bathroom, garage, outdoor
30A	10 AWG	Electric dryer, water heater
40A	8 AWG	Electric range (small), heat pump
50A	6 AWG	Electric range (large), hot tub
60A	4 AWG	Sub-panel feed, EV charger (48A)
100A	2 AWG or 1/0 AWG	Sub-panel feed, large loads

This chart is non-negotiable. You cannot use a larger breaker than the wire allows.

The 80% Rule

CEC Rule 8-104 says continuous loads (running more than 3 hours) should not exceed 80% of the breaker rating:

Breaker	80% Continuous Load	Apply To
15A	12A	Lighting circuits running all day
20A	16A	Kitchen circuits, space heaters
30A	24A	Water heaters, dryer

This means a 15A circuit with LED pot lights running 8+ hours should not draw more than 12A continuously.

How to Calculate Your Load

Watts ÷ Volts = Amps

Example: Kitchen Counter Circuit

• Toaster: 1,200W
• Kettle: 1,500W
• You'd never run both simultaneously on the same circuit, but either alone:
• 1,500W ÷ 120V = 12.5A → Needs 20A circuit (12 AWG)

Example: Lighting Circuit

• 12 LED pot lights at 12W each = 144W total
• 144W ÷ 120V = 1.2A → Easily fits on a 15A circuit (14 AWG)
• A 15A circuit could theoretically power ~100 LED pot lights (but code limits wiring practicality)

Example: Electric Dryer

• Typical: 5,400W at 240V
• 5,400W ÷ 240V = 22.5A → Needs 30A circuit (10 AWG, 2-pole breaker)

Dedicated vs Shared Circuits

Some circuits must be dedicated (serving only one appliance or outlet):

Must Be Dedicated	Breaker	Wire
Dishwasher	20A	12/2
Microwave (built-in)	20A	12/2
Refrigerator	15A or 20A	14/2 or 12/2
Garbage disposal	20A	12/2
Washer	20A	12/2
Dryer	30A	10/3
Range/oven	40A or 50A	8/3 or 6/3
Furnace	Per nameplate	Per nameplate
Hot tub	40A-60A	Per nameplate

Shared circuits (multiple outlets on same breaker) are allowed for general lighting and receptacles in bedrooms, living rooms, etc.

Special Breaker Types

AFCI (Arc Fault Circuit Interrupter)

Required by CEC for:

• All bedroom circuits (15A and 20A)
• Recommended for living rooms and hallways

Our Combination AFCI Breaker - 15A provides both arc fault and overload protection.

GFCI (Ground Fault Circuit Interrupter)

Required for:

• Bathroom receptacles
• Kitchen counter receptacles (within 1.5m of sink)
• Outdoor receptacles
• Garage receptacles
• Unfinished basement receptacles

Can be provided by a GFCI breaker at the panel or a GFCI receptacle at the outlet.

What to Buy

Product	Size	Price
Single Pole Breaker 15A	15A	$8.99
Single Pole Breaker 20A	20A	$9.49
Double Pole Breaker 30A	30A	$16.99
AFCI Breaker 15A	15A	$44.99
GFCI Receptacle 15A	15A	$14.99

Available at our Brampton showroom or online at saferlighting.ca.

Not sure what breaker you need? Safer Electric (ESA Licence #7008996) can assess your panel and install the correct breakers for your circuits. Call (647) 383-9500.

FAQ

My breaker keeps tripping. Should I install a bigger one? No. A tripping breaker means the circuit is overloaded or there's a fault. Installing a larger breaker is extremely dangerous — it removes the protection the breaker provides. Reduce the load or have an electrician add a new circuit.

Can I replace a 15A breaker with a 20A? Only if the entire circuit is wired with 12 AWG (or larger) wire. If any wire on the circuit is 14 AWG, you must keep the 15A breaker.

How many outlets can I put on a 15A circuit? The CEC doesn't set a maximum number of outlets per circuit, but the total load on the circuit must not exceed the breaker rating. A practical guideline is 8-12 outlets on a 15A circuit for general-use rooms.

What is the difference between a single pole and double pole breaker? Single pole breakers protect 120V circuits (one hot wire). Double pole breakers protect 240V circuits (two hot wires) for appliances like dryers, ranges, and air conditioners.