01 / Short answer
A 1,500 W heater covers about 150 sq ft.
A common rule of thumb is about 10 watts per square foot of floor for a typical room with 8 ft ceilings. Plug-in heaters for standard 120 V outlets top out at 1,500 W, so one heater suits a bedroom or office, not an open-concept main floor. Drafty rooms and higher ceilings need more.
02 / Calculator
Size a heater for your room.
Measure the floor from wall to wall. Leave ceiling height blank for a standard 8 ft (2.4 m) ceiling.
For a typical room with 8 ft ceilings. Adjusted below for insulation and ceiling height.
Enter the room's length and width. This sizes supplemental heat for one room, not a whole-home heating system.
03 / How it works
Three numbers decide the size.
About 10 W per sq ft
The calculator uses 8 W per sq ft for well-sealed rooms, 10 for typical rooms and 12 for drafty ones, the range most sizing guides give.
Taller rooms hold more air
The estimate rises in proportion to ceiling height above 8 ft: a 10 ft ceiling needs about 25% more, a 12 ft ceiling about 50% more.
One outlet, one heater
A 1,500 W heater draws about 12.5 A on a 120 V outlet, most of a standard 15 A household circuit. Two big heaters on one circuit can trip the breaker.
04 / Safety
Five checks before you plug it in.
- 01
Look for a Canadian certification mark
Choose a heater labelled by a certification body recognized in Canada, such as CSA, cUL or ULC. Imports from third-party sellers may not carry one.
- 02
Plug straight into the wall
Extension cords and power bars aren't built for the current a space heater draws. Technical Safety BC warns against using them.
- 03
Get tip-over and overheat shut-off
These cut power if the heater falls over or runs too hot, which matters around children and pets.
- 04
Keep the clearance in the manual
Keep curtains, bedding, furniture and paper away from the heater by at least the distance the manufacturer specifies.
- 05
Unplug it when you leave
Turn it off and unplug it when you leave the room or go to sleep, unless the manual says it's designed for unattended use.
05 / Types
Match the heater to how you use the room.
Oil-filled radiator
Slow to warm up, silent, and keeps giving off heat after it cycles off. Good for bedrooms and all-evening use.
Ceramic fan heater
Warms the air quickly and is easy to move, with some fan noise. Good for short bursts in a bathroom or office.
Infrared heater
Warms people and objects in its path rather than all the air. Good for a cold corner or desk.
06 / Heaters to compare
Two common types.
Each link opens an Amazon.ca search for the product. Check the wattage, certification mark and safety shut-offs on the listing. More in the home buying guide.
De'Longhi Dragon oil-filled radiator heater
An oil-filled radiator: silent, slow to warm up, and keeps radiating after it cycles off. Suits bedrooms and long, steady use.
Dr Infrared Heater portable space heater
An infrared heater with a fan: warms people and objects in front of it quickly. Suits a cold corner or home office.
07 / Quick answers
Common questions.
What size space heater do I need for a 12 by 12 room?
About 1,440 W for a typical room with 8 ft ceilings, using the rule of about 10 W per square foot. One 1,500 W heater on its high setting should cover it.
How many square feet does a 1,500 W heater heat?
About 150 square feet in a typical room with 8 ft ceilings. A drafty room or a higher ceiling lowers that, to about 125 square feet at 12 W per square foot.
How many BTUs is a 1,500 W space heater?
About 5,100 BTU per hour, since one watt is about 3.412 BTU per hour.
Can I plug a space heater into an extension cord?
No. Technical Safety BC warns that extension cords and adapters can't handle the energy a space heater draws. Plug it straight into a wall outlet.
Can I run two space heaters on one circuit?
Usually not. One 1,500 W heater draws about 12.5 A on a 120 V outlet, most of a standard 15 A household circuit, so a second heater on the same circuit can trip the breaker.
08 / Sources