That grey metal box in your basement or utility room is the nerve centre of your home's electrical system. Most homeowners interact with it exactly twice: when they move in, and when something trips. Here's everything you need to understand about your panel — without the electrical engineering degree.
The basics: what your panel actually does
Your home receives electricity from the utility company through a service entrance — the wires that come from the street into your panel. The panel's main breaker controls all power to your home. Below it, individual circuit breakers distribute that power to different parts of your home, each protecting a specific group of outlets, lights, or appliances.
Think of it like a water main with a series of smaller valves. The main breaker is the master valve; each circuit breaker is a smaller valve controlling one branch of the system. If too much water flows through one branch (too much current), the valve shuts off automatically to prevent the pipe from bursting (the wire from overheating).
What does the amperage rating mean?
Your main breaker will have a number on it — typically 100A, 150A, or 200A. This is your home's total service capacity. It means your home can draw up to that many amps from the utility at once. A 200A service is standard for modern Canadian homes.
In practice, you'll never run everything simultaneously, so a 200A panel provides ample headroom. Older GTA homes often have 100A service — enough for the electrical loads of the 1960s, but tight for modern households with EVs, central air, and large appliances.
15-amp vs. 20-amp circuits: what the difference means
Each breaker controls one circuit. The breaker's amperage rating limits how much current that circuit can safely carry. A 15A breaker protects a 14-gauge wire rated for 15 amps. A 20A breaker protects a 12-gauge wire rated for 20 amps.
- 15-amp circuits: lighting, standard bedroom outlets, small general-purpose loads
- 20-amp circuits: kitchen countertops, bathrooms, laundry, home office equipment
- Dedicated circuits (often 20A or higher): dishwasher, microwave, refrigerator, dryer (240V/30A), EV charger (240V/40A+)
Single-pole vs. double-pole breakers
Single-pole breakers take up one slot in the panel and protect 120V circuits — the standard circuits for most of your home. Double-pole breakers take up two slots (they're visibly wider, with a single handle) and protect 240V circuits — your dryer, electric range, air conditioner, water heater, and EV charger.
Why does my panel have empty slots?
Empty slots (or 'spaces') in your panel mean you have room to add circuits in the future — finishing a basement, adding an EV charger, or installing a hot tub. If your panel is completely full and you need to add circuits, you have options: a tandem (double) breaker in some slots, a subpanel, or a full panel upgrade.
The one thing you should never do to your panel
Never replace a breaker with a higher-amperage one to 'fix' frequent tripping. If a 15A breaker trips regularly, that's because the circuit is drawing more than 15A. Installing a 20A breaker doesn't fix the overload — it just lets the wire overheat without tripping. The wire is still rated for 15A. This is how electrical fires start.
Once a year, flip your main breaker off and back on. This exercises it and keeps the contacts clean. Do the same with any individual breakers that seem stiff. A breaker that won't reset (or resets but immediately trips again) needs replacement.
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.