Load calculation: are your 100 A enough?

How the calculation works

• Living area: measured inside the exterior walls, 100% of the ground and upper floors, 75% of the basement.
• Basic load: 5,000 W for the first 90 m², plus 1,000 W for each additional 90 m² or part of it. It covers lighting and outlets.
• Heating: with baseboards and a thermostat in each room, 100% of the first 10 kW and 75% of the rest; an electric furnace counts at 100%.
• Air conditioning: 100%. An air conditioner does not run at the same time as the heating: the larger of the two is used.
• Heat pump: 100%, plus the electric backup heat, unless an interlock prevents them from running together.
• Range: 6,000 W, plus 40% of the amount over 12,000 W.
• Tankless water heater, hot tub, whirlpool, pool heater: 100%.
• EV charger: 100%, whether installed or only planned, except with a load management system.
• Other appliances over 1,500 W (tank water heater, dryer): 25% if there is an electric range; otherwise 100% up to 6,000 W, then 25%.
• Result: the total in watts divided by 240 V gives the minimum service rating, never less than 100 A for a home of 80 m² or more, basement excluded.

Checked against the Régie du bâtiment example: a 306 m² home with 15,000 W of baseboards, a 14,000 W range, a hot tub, a tankless water heater, a dryer, a water heater and an air conditioner gives 56,675 W, or 236 A.

Sources

• Order 236-2026: Regulation amending the Construction Code (Chapter V, Electricity), Gazette officielle du Québec, March 11, 2026 (in French) (new tab)
• Quality control of electrical installation work, Régie du bâtiment du Québec (worked example, section 8-200, in French) (new tab)
• Electricity: laws, regulations and codes, Régie du bâtiment du Québec (new tab)