Most homeowners have never opened their electrical panel. It lives in a utility room or closet, the door stays shut, and it quietly does its job until something trips. But your panel tells you a lot about your home's electrical system — its capacity, its age, whether it's a brand with known problems, and whether the previous owners made decisions that affect your safety today. Here's how to read what's in front of you.
Quick Answer
Open your panel door and look at the large double breaker at the top — that's your main breaker. The number stamped on it (100, 150, or 200) is your service amperage. The brand name on the panel door or breakers tells you the manufacturer. The date is usually on a label inside the door or stamped on the panel itself. If you see Federal Pacific, Zinsco, or mismatched breaker brands, call a licensed electrician.
Step 1: Identify Your Service Size — 100A or 200A
Your panel's service size tells you the maximum current your home can draw from the utility. It's determined by the size of the service entry cable coming in from the street and the rating of your main breaker.
How to find it: Open the panel door. At the very top of the breaker rows, there will be a large double-pole breaker — usually wider than the others and often positioned alone. The number stamped or printed on that breaker handle is your service amperage:
60A Service
Rare today but found in some pre-1960s Toronto homes, often alongside a fuse box or very early breaker panel. This is not adequate for modern electrical demand and should be upgraded. If you have 60A service, you likely also have a fuse box.
100A Service
Common in Toronto homes built from the 1960s through the 1990s. Functional for a home with mostly gas appliances — gas furnace, gas water heater, gas stove, gas dryer. Once you add electric appliances, central AC, or an EV charger, 100A becomes a constraint. A single Level 2 EV charger drawing 40A on a 100A service leaves very little headroom for the rest of the home.
150A Service
Less common but found in some mid-range renovations and additions. Often a stepping stone between 100A and 200A. Better than 100A but may still be limiting for homes adding EV charging alongside a heat pump.
200A Service
The current standard for new residential construction in Ontario. Supports modern electrical loads including EV chargers, heat pumps, electric dryers, central AC, and all modern appliances simultaneously. If you're renovating or adding major loads, this is where you want to be.
Can't find the main breaker? Some Toronto homes have the main disconnect located outside near the meter in a separate weatherproof enclosure, not inside the panel. If there is no large breaker at the top of your panel, your outside disconnect is controlling the service. The amperage is still stamped on that exterior breaker.
Step 2: Identify the Brand
The manufacturer's name is usually printed on the panel door, the interior backplate, or the breakers themselves. This matters — some brands have documented safety issues and others are considered industry-standard premium products.
Here are the brands you're most likely to encounter in Toronto homes:
Trusted / Premium Brands
Square D (QO Series)
One of the most respected panel manufacturers in North American residential construction. Square D QO (Qwik-Open) breakers use an all-plug-in design and a fast trip mechanism that opens the full breaker width — not just a partial release. They are known in the trade for reliable operation, minimal nuisance tripping, and longevity. The QO series has been in production since the 1950s with a consistent and well-supported breaker format. If you have a Square D QO panel, you have a good panel.
Siemens
A reliable European-origin brand with a strong track record in North American residential and commercial applications. Siemens panels are well-regarded and commonly installed in newer Toronto homes and renovations. Breakers are plug-on and clearly labeled. A Siemens panel is a good panel.
Eaton (Cutler-Hammer)
Eaton's residential line — formerly sold as Cutler-Hammer — is another reliable option common in Canadian residential construction. Their CH and BR series breakers are widely used and well-supported. If you have an Eaton panel, you're in good shape.
Leviton (Load Centre)
A newer entrant to the residential panel market but with solid quality and growing adoption in Canadian new construction. Reliable and code-compliant.
Problem Brands — Replace These
⚠ Federal Pacific Electric (Stab-Lok)
Federal Pacific panels are the most commonly flagged problem panel in Toronto and across North America. The Stab-Lok breakers have a documented history of failing to trip under overload conditions — meaning the circuit protection doesn't work as intended. Studies have found significant failure rates in field testing. These panels are flagged by Ontario home insurance companies and are recommended for replacement. If you see an orange or red Stab-Lok logo inside the panel, this is a Federal Pacific.
⚠ Zinsco / GTE-Sylvania
Zinsco breakers can fail to trip and in some documented cases have welded themselves into the ON position — meaning a breaker that has tripped can appear to reset but remains live. They also have known issues with bus bar corrosion. Like Federal Pacific, Zinsco panels are flagged by Ontario insurers and should be replaced.
⚠ Pushmatic (ITE / Bulldog)
Pushmatic panels use a push-on/push-off mechanism instead of the standard toggle switch. The panels are no longer manufactured, replacement breakers are increasingly difficult to source, and the breakers require manual monthly exercising to maintain reliable operation. While not in the same danger category as Federal Pacific, they are aging out and replacement is recommended when encountered.
Step 3: Estimate the Age of the Panel
Panel age matters for two reasons: it tells you approximately how much service life remains, and it can help flag panels installed during eras when certain problematic brands were common.
How to find the age:
- Date sticker inside the door — many panels have a label applied by the installer or inspector with the installation date.
- Manufacture date on the panel body — look on the interior backplate or the inside of the door for a stamped or printed date code.
- ESA inspection sticker — if the panel was inspected by the Electrical Safety Authority after installation, there may be a sticker with the inspection date.
- Building permit date — if the home's original electrical was permitted, that date approximates the panel's installation year.
A well-maintained panel from a quality manufacturer can last 40+ years. A panel from a problematic manufacturer should be replaced regardless of age. A panel of any brand showing physical deterioration — rust, burn marks, melted plastic, loose breakers, or evidence of water intrusion — should be assessed immediately.
Breaker Brand Mixing: A Common and Serious Problem
Every panel manufacturer designs their breakers to work with their specific bus bars — the copper rails that carry current through the panel. The fit, connection pressure, and trip characteristics are calibrated for that specific combination.
Mixing breaker brands is not a small issue. A Siemens breaker installed in a Square D panel, or a generic breaker installed in an Eaton panel, is:
- Not tested or listed for that combination — it has not passed safety testing in that panel.
- Potentially unreliable — the trip characteristics may be wrong, causing the breaker to trip too early, too late, or not at all.
- A code violation — the Ontario Electrical Safety Code requires breakers to be listed and approved for the panel they're installed in.
A note from the field: Mixed breakers are common in older Toronto panels — especially after years of piecemeal additions by different electricians or handymen. We see Siemens breakers in Cutler-Hammer panels, generic breakers in Square D panels, and combinations that have clearly never been reviewed by anyone. Open your panel and check: every breaker should carry the same brand name as the panel itself.
The only exception is listed "classified" breakers — certain manufacturers produce replacement breakers explicitly listed and tested for use in other manufacturers' panels. These are labeled clearly as compatible replacements and are a legitimate option in specific situations. They are not the same as simply using a breaker from a different brand and hoping it fits.
Panel Labelling: Required, Practical, and Often Missing
The inside of every breaker panel door has a directory — a list of which breaker number controls which circuit. It might say "Kitchen counter outlets," "Master bedroom," "Basement lights," or "Furnace." That directory is not optional — the Ontario Electrical Safety Code requires panels to be labelled so that circuits can be identified.
In practice, panel labelling in older Toronto homes ranges from incomplete to completely blank. This creates real problems:
- Emergency situations — if a circuit is sparking or a wire is exposed and you need to shut off power immediately, you can't afford to guess. An unlabelled panel means guessing or shutting off the main.
- Renovations and electrical work — any electrician working in your home has to trace circuits manually if the panel isn't labelled, adding time and cost to every job.
- Safe DIY work — even basic tasks like replacing an outlet require knowing which breaker to turn off. Mislabelled panels lead to people working on live circuits.
- Selling the home — a home inspection will note a mislabelled or unlabelled panel. It's a simple thing to fix before listing.
How to Label Your Panel Properly
Labelling a panel means turning off one breaker at a time and checking which outlets, lights, and appliances go dead. A two-person job makes this faster — one person at the panel, one person walking the home. Once identified, write the circuits clearly on the panel directory (a pencil is fine — labels can be updated as you add circuits). Be specific: "Kitchen counter — south wall" is more useful than "Kitchen." If you'd like it done professionally and thoroughly during any electrical service call, we include circuit labelling as part of the job.
What a Healthy Panel Should Look Like
Warning Signs That Need Attention
Common Questions
How do I know if I have 100A or 200A service?
Look at the main breaker — the large double-pole breaker at the top of the panel. If it's labelled 100, you have 100A service. If it's labelled 200, you have 200A service. If there is no main breaker visible, your disconnect may be located outside near the meter. When in doubt, a licensed electrician can confirm your service size in minutes.
Is a 100A panel enough for a Toronto home?
A 100A panel is functional for smaller homes with gas appliances — furnace, water heater, stove, and dryer all on gas. Once you add electric appliances, central air conditioning, an EV charger, or a heat pump, 100A service often becomes a limiting factor. Many Toronto homes upgrading to EVs or heat pumps are simultaneously upgrading to 200A service.
Are Federal Pacific and Zinsco panels dangerous?
Yes. Both Federal Pacific (Stab-Lok) and Zinsco panels have documented histories of breakers failing to trip under overload conditions. A breaker that doesn't trip cannot protect your wiring. Ontario insurance companies flag these panels, and replacement is strongly recommended regardless of the panel's age.
Can I mix breaker brands in my panel?
No. Breakers must match the panel manufacturer. A Siemens breaker installed in a Square D panel is not tested or listed for that combination. Mismatched breakers can fail to trip correctly or may not seat properly. If you see mixed brands in your panel, it should be corrected by a licensed electrician.
What is a Square D QO panel and why is it considered premium?
Square D QO (Qwik-Open) breakers use an all-plug-in design with a visible trip indicator and a very fast trip mechanism. They are known in the trade for low nuisance tripping and reliable performance over decades of use. Square D is one of the most respected panel manufacturers used in Canadian residential construction.
Why does panel labelling matter?
Accurate panel labelling tells you — and your electrician — exactly which breaker controls which circuit. In an emergency, mislabelled or unlabelled panels mean wasted time finding the right breaker, or worse, working on a circuit that is still live. Ontario Electrical Safety Code requires panels to be labelled. If yours isn't, it should be.
Not Sure What You're Looking At?
Portman Electric can assess your panel, identify problem brands, check for mixed breakers and double-tapping, label your circuits, and give you an honest picture of whether your panel needs attention. We service Toronto and the GTA — no upselling, just a straight assessment.
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