Three calls last week — same problem, different addresses. Burlington, Ancaster, west Hamilton. Each one a homeowner whose panel had been fine for years until a stretch of plus-32 days in August finally pushed it past tolerance. The pattern is identical: AC is running flat out, pool pump is running, EV is charging, somebody starts the dryer, the main trips at 4pm. Reset the main and it works again until the next afternoon. Here is what is actually going on and what the options are.
Why the panel trips on a hot day specifically
A panel does not just trip on amperage. It trips on heat. The main breaker has a thermal element that responds to current over time. At 25°C ambient inside the panel cabinet, a 100A breaker will hold close to 100A indefinitely. At 45°C ambient (what an unventilated south-facing utility room hits on a 33°C summer day) that same breaker will trip at 85-90A. The breaker is doing exactly what it should. Your service is at limit, and the heat is the variable that pushed it over.
The continuous-load math under heat-wave conditions on a typical Burlington home:
- AC condenser, 3.5 ton, running flat out. 24A at 240V continuous, plus inrush.
- Pool pump, single-speed. 8-10A at 240V continuous when running.
- EV charger, 32A Level 2. 32A at 240V continuous.
- Dryer running. 25A at 240V cyclic.
- Range, two burners + oven. 30A at 240V cyclic.
- Everything else (lighting, fridge, freezer, electronics). 15-20A spread across 120V.
Add the continuous loads with the 125% continuous-load multiplier and you are at 90-100A before the cyclic loads start. Pick a moment when the dryer and the oven both happen to be running while the AC is on and you are at 130-140A momentary on a 100A service. The breaker holds for a while, the cabinet heats up, the breaker holds less. Eventually it trips.
The three real options
Once we have measured the actual draw at the panel and confirmed the diagnosis (we use a clamp meter on the service entrance over a few hours), the options are:
- Service upgrade to 200A. The structural answer. New main breaker, new service-entrance conductor, new meter base if needed, ESA permit and inspection. Most 100A-to-200A residential upgrades are a one-day job and we coordinate the utility disconnect. After this, the same load that was tripping the panel runs at 35-50% of capacity with comfortable headroom. Detail in our service upgrade page.
- Load management. Keep the 100A service, add a smart load management device that prevents the EV charger and the AC and the dryer from all running at peak together. Cheaper than a service upgrade, but the EV charging gets paused during the AC's hot afternoon run. Manufacturer-supported (Tesla, ChargePoint, Wallbox all offer this) or with a separate device like a Span or DCC.
- Smart panel. Replace the existing panel with a smart panel (Span, Lumin) that monitors and controls every circuit individually. Expensive, but lets you set load priorities and shed lower-priority circuits automatically when the service approaches limit. Best for households planning multiple electrification upgrades over the next few years.
Why we lean toward service upgrade in most cases
Load management works. We install it for the right households. But the cases where it is the best answer are narrower than the cases where a service upgrade is. The reasons:
- A 100A service in 2027 is undersized for any electrification path forward. Heat pump, EV, induction range, electric water heater — pick two and you are at limit. The trend is toward more electrification, not less.
- Service upgrades are paid once. Load management is a workaround with operational cost (you live with reduced EV charging speed during peak afternoons).
- The price difference is meaningful but not enormous. A smart load manager plus install runs a meaningful fraction of what a service upgrade runs. For a household that will be in the house another 10+ years, the upgrade math usually wins.
- Insurance and resale. A 200A service is what every newer Burlington and Oakville home has. A 100A service with workarounds is going to be a discussion item on a future home inspection.
When load management is the right call
- You are planning to sell inside 2-3 years and the buyer can deal with it.
- The service-entrance run from the pole or pad to the house would be expensive (long underground run, finished landscape to tear up, transformer needs upgrading on the utility side).
- You have a single specific conflict (usually EV charging versus everything else) and resolving just that one is enough.
- The existing panel is in good condition (not FPE Stab-Lok, not Federal Pioneer, not aluminum-bus Zinsco) and otherwise has 5-10 years of life left.
What we measure before quoting
We do not recommend a service upgrade without measuring the actual load. The diagnostic visit covers:
- Clamp-meter readings at the service entrance over a 30-60 minute window during likely peak (afternoon, AC running).
- Panel cabinet temperature reading.
- Visual inspection of every breaker for heat damage, loose lugs, or discoloration.
- Service-entrance conductor inspection at the meter base.
- Bonding and grounding check.
- Inventory of installed loads with their nameplate amperage.
- Formal load calc against the OESC demand factors.
Output is a written quote with two options where it makes sense — service upgrade priced, load management priced, and the trade-offs called out.
The smart-panel question
We have installed a handful of Span panels in 2026-2027 across higher-end Burlington and Oakville builds. Verdict: the technology works. The app is good. The load-shedding actually shifts charging away from peak. The price is what it is.
For a household actively building out battery storage, solar, multiple EVs, and a heat pump, the smart panel is the right architecture. For a household that just wants the AC and the EV to coexist on a 100A service, it is overspec'd. Service upgrade is cheaper and gives you the same operational headroom.
When to call us
If your main is tripping during heat waves, the AC is cycling oddly, or you are planning to add a pool, an EV, or a heat pump to a 100A panel, we do this service upgrade work routinely across Hamilton, Burlington, Waterdown, Ancaster, Dundas, Stoney Creek, and Oakville. Request a quote with a panel photo and a list of major appliances. If load management gets you there without the upgrade, that is what we will recommend.