TL;DR
A 100A panel is genuinely enough for about 70% of the Montréal homes we audit. Including most homes with an EV charger. The number that matters isn't the breaker rating, it's your continuous load. Here's how to actually calculate it, with a real example.
About once a week a homeowner tells me their last electrician quoted a panel upgrade because “100 amps just isn't enough anymore.” Sometimes that's true. More often it's a $4,500 conversation that should've been a 20-minute load calculation.
The myth · “you need 200A”
There's a strain of advice in the trade. And on every contractor forum. That defaults to recommending 200A any time someone mentions an EV, a heat pump, or an induction range. The thinking goes: more capacity is safer, and the homeowner pays for it, so why not.
Two reasons why not. First, it costs the homeowner $3,000–$7,000 in work they probably don't need. Second, the Hydro-Québec service entrance upgrade. The meter base and the supply from the pole. Is a real project with permits, inspections, and possible disruption. Doing it because someone didn't want to do math isn't fair.
The actual math · CEC Section 8
The Canadian Electrical Code defines a residential load calculation in Section 8. We use the standard residential method (8-200(1)(a)) for any home under 80m². It boils down to:
- Basic load: 5,000W for first 90m², plus 1,000W per additional 90m².
- Heating + HVAC: 100% of the largest (heat or cool).
- Range / oven: 6,000W if rated under 12kW.
- Water heater: 100% of nameplate.
- EV charger: 100% of continuous output.
- Other loads (dryer, dishwasher, pool, hot tub): nameplate values, with diversity factors.
Add them up. Divide by 240V to get amps. Compare to the panel's continuous rating (80% of breaker).
A 100A panel can host 80A continuous. That's 19,200W. A surprising number of homes. Gas heat, gas range, modest hot water. Sit well under that even with an EV.
Pierrefonds bungalow · August 2026
Real audit, anonymised. 1,400 sq ft bungalow, built 1973, original 100A panel, owner wanted a Tesla Wall Connector at 40A continuous.
- Basic + 90m². 5,000W + 1,000W (130m²) = 6,000W
- Electric baseboard (winter). 8,400W
- Electric range. 6,000W (nameplate 9.6kW, under 12kW rule)
- Water heater. 4,500W
- Dryer. 5,000W
- EV charger. 9,600W (40A × 240V)
Total: 39,500W. Divided by 240V = 164A nameplate.
Now apply diversity (the code knows you don't run everything at once): basic at 100%, heating at 100%, the next-largest load at 65%, and so on. After diversity: 74A continuous. Comfortably under the 80A continuous limit of a 100A panel.
That homeowner got their Tesla install, kept their existing panel, and saved $4,200 vs the upgrade quote they had in hand.
When a 100A panel genuinely needs upgrading
- Continuous load over 80A after diversity. Usually all-electric homes with EV + heat pump + induction.
- Federal Pacific, Zinsco, or Sylvania-Challenger panel. Insurance risk, replace regardless of capacity.
- Aluminum branch wiring running into a panel with no AL-rated breakers. Service rework, not just upgrade.
- No physical room for a double-pole breaker, with no sub-panel possibility. Sometimes the panel is just full.
- Service entrance over 50 years old with visible insulation degradation. Independent of capacity.
When you're being told to upgrade and shouldn't
- “You can't add an EV to a 100A panel.”. Not true 70% of the time.
- “200A is the modern standard.”. It's not standard. It's adequate for the maximum case.
- “Insurance won't cover you.”. They only care about the panel brand and condition, not the rating.
- “Resale value.”. A clean 100A with a proper load calc on file beats a 200A done lazily.
Get an audited quote
If you've been quoted a panel upgrade and want a second opinion, we'll do the load calc for free. About a third of the time we end up recommending the upgrade. And we'll tell you why. The other two thirds we save you the work.
Second opinion · free load calc.
Bring the quote you have in hand. We'll do the math on paper, in front of you, in about 20 minutes.
