CEC Part I · Section 8
Service Size Calculator
Given your home's estimated demand load, see which standard Ontario service size — 100A, 125A, 150A, 200A, or 400A — actually fits, with headroom.
1. Demand Load
2. Recommended Service
Ontario standard sizesMINIMUM SERVICE SIZE
— A
HEADROOM AT THIS SIZE
— A
Note: Enter your demand load to see a recommendation.
This is an educational estimate. Actual service sizing must come from a proper CEC Section 8 load calculation completed by a licensed electrician, and any service change always requires an ESA permit.
Common Ontario service sizes, roughly explained
- 100A — the long-standing standard for many existing homes; can be tight once EVs, heat pumps, or electric ranges are added.
- 125A / 150A — a middle ground, sometimes used where 100A is outgrown but a full 200A upgrade isn't needed yet.
- 200A — the current standard for new construction and most major renovations, with comfortable headroom for electrification.
- 400A — typically reserved for very large homes or homes going fully electric with multiple EVs, heat pumps, and other major loads.
What feeds the house
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