Renovation · CEC Section 62 (Fixed Electric Space Heating)

Electric Heater Load Calculator

Size circuit breakers and conductors for baseboard heaters, fan-forced wall heaters, and garage unit heaters using the mandatory CEC 80% continuous heating rule.

1. Electric Heating Loads

Supply Voltage

Total Connected Heater Wattage

2. Heating Circuit Results

CEC Section 62 80% Rule

NOMINAL HEATER CURRENT

12.5 Amps

MINIMUM BREAKER RATING (125%)

20A 2-Pole Breaker

MINIMUM COPPER NMD90 WIRE

12/2 NMD90 (Red & Black)

CEC Section 62 Rule: Electric space heating is a continuous load. Maximum allowable wattage on a 20A 240V circuit is 3,840 Watts (80% of 4,800W).

CEC Section 62 Heating Rules

Baseboard heater circuits must not exceed 80% of the branch circuit rating (e.g. 2,880W max on 15A 240V, 3,840W max on 20A 240V).
Baseboard heaters must not be installed directly below electrical wall receptacles per CEC Rule 62-118.
Line-voltage thermostats break both ungrounded hot conductors or have a marked OFF position for safety isolation.

Baseboard sizing rule of thumb (10 W/ft²)

For 240 V baseboard in a reasonably insulated room.

Room area	Heater watts	Amps @ 240 V	Min. breaker
8×10 ft (80 ft²)	800–1,000 W	3.3–4.2 A	15 A
10×12 ft (120 ft²)	1,200–1,500 W	5–6.3 A	15 A
10×15 ft (150 ft²)	1,500–2,000 W	6.3–8.3 A	15 A
12×20 ft (240 ft²)	2,400–3,000 W	10–12.5 A	15–20 A
16×20 ft (320 ft²)	3,200–4,000 W	13.3–16.7 A	20 A

High ceilings, poor insulation, or large windows push sizing up. Thermostats switch the full load — use ones rated for the amperage.

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