Extension cords, power bars and space heaters in winter

Winter puts circuits to the test

When it is -30 C outside, a cold basement bedroom or drafty home office is a good reason to plug in a space heater. Add holiday lights, block heaters and a kettle that never seems to stop, and many household circuits spend the winter close to their limit.

Space heaters, extension cords and power bars are useful. They are also behind a lot of preventable house fires every winter. Most of the risk comes down to two things: putting too much load on a circuit or cord, and putting heat too close to things that burn.

How much a space heater really draws

A typical plug-in space heater on its high setting uses about 1500 watts. On a 120 V circuit that works out to about 12.5 amps, which is most of what a common 15 A circuit can supply.

Heaters also run for hours at a time. For loads that run continuously, the code generally limits them to 80 percent of the circuit rating, which is 12 A on a 15 A circuit. That is why one heater plus almost anything else on the same circuit can trip the breaker.

Space heater safety

• Plug it directly into a wall receptacle. Never use an extension cord or power bar for a space heater.
• Keep at least one metre of clear space around it: curtains, bedding, furniture, paper and clothes.
• Choose a model with tip-over and overheat shut-off, certified for use in Canada (look for a CSA, cUL or cETL mark).
• Turn it off when you leave the room or go to sleep.
• Check the plug and receptacle. If either feels hot, or the plug is loose in the outlet, stop using it and have the receptacle checked.
• One heater per circuit. Do not run two heaters on the same circuit.

Extension cords and power bars

Extension cords are meant for temporary use. When they become permanent, they get pinched under doors, run under rugs, stepped on and overloaded.

• Match the cord to the load. Check the amp or watt rating on the tag and make sure it exceeds what you plug in.
• For outdoor use, including block heaters and holiday lights, use a cord marked for outdoor use (look for a W in the type, such as SJTW) and rated for cold temperatures.
• Never run cords under rugs, through doorways or windows, or where they can be pinched.
• Do not chain extension cords or plug one power bar into another.
• Uncoil cords fully when they carry a heavy load. A coiled cord holds in heat.
• Throw out cords with cracked jackets, damaged plugs or a missing ground pin.

Power bars with surge protection are great for electronics, but they do not add capacity. Everything on a power bar still comes from one receptacle on one circuit. For whole-home protection from surges, see surge protection.

Holiday season and other peak times

December is when circuits work hardest. Indoor trees, outdoor displays, extra cooking and guests all add load at the same time as the furnace and space heaters.

• Switch old incandescent light strings to LED. They draw a fraction of the power.
• Spread decorations across several circuits instead of running everything from one receptacle.
• Use timers so displays are not running all night.
• Keep cords away from the tree's water stand and from heat sources.
• Check your smoke alarms before the season starts. See hardwired smoke and CO alarms.

If a breaker trips while you are decorating, take that as a sign the circuit is full, not a problem to work around.

When it is time for a better fix

If you rely on a space heater every winter, or have extension cords running across rooms, your home is telling you something. Better long-term options include:

• A new dedicated circuit or more receptacles where you actually need them.
• Permanent electric baseboard heating or in-floor heating for a cold room or basement.
• A heat pump to improve comfort across the home.
• Checking your panel and service capacity before adding big loads.

A licensed electrician can look at how your circuits are loaded and suggest the simplest safe fix.

Common questions