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.