When to Plug In Your Block Heater in Canada: Temperature, Timer and How Long

Quick answer: Plug in your block heater once it drops below -5°C, says CAA-Quebec, and do not skip it at -15°C or colder. You do not need to plug in all night. NRCan says a timer that turns on two hours before you drive is usually enough. CAA-Quebec says three to four hours.

Key takeaways

• CAA-Quebec says plug in below -5°C. It strongly recommends it at -15°C or colder.
• NRCan says two hours on a timer is usually enough. CAA-Quebec says three to four hours.
• NRCan says a block heater can improve fuel economy by as much as 10% at -20°C.
• Use a three prong extension cord made for outdoor use, plugged into a GFCI outlet, says Ontario's Electrical Safety Authority.
• A remote starter warms the cabin, not the engine. CAA-Quebec says it is not the same thing.

What a block heater does to your engine on a cold morning

A block heater is a small electric heater in your engine. Most of them warm the coolant. The warm coolant then warms the engine block and the oil.

NRCan explains why this matters. In a cold engine, the oil is thick and does not flow well. The engine has to work harder. It also burns a richer mix of fuel, and the catalytic converter does not work well until it warms up. So the first minutes after a cold start use more fuel and make more pollution.

With a block heater, the engine starts more easily and reaches its normal temperature faster. In my years around cars and shops, the plugged in car is almost always the one that starts on the first try at -25°C.

Photo: Banjodog, CC BY-SA 4.0, via Wikimedia Commons

What temperature should you plug in your block heater?

Here is the rule I give people, and it comes straight from CAA-Quebec:

• Below -5°C: plug in.
• At -15°C or colder: plug in for sure. CAA-Quebec calls this highly recommended.

Your owner's manual may give its own number. Some diesel trucks, for example, list a set temperature in the cold weather section. If your manual says something different, follow the manual for your vehicle.

How long to plug in a block heater before you start the car

You do not need to leave it plugged in all night. That only adds to your power bill.

• NRCan: use a timer that turns the heater on two hours before you drive. NRCan says this is usually all the time needed to warm the coolant and the engine.
• CAA-Quebec: three to four hours before you leave is enough.

So two to four hours is the window. On the coldest mornings of the year, I lean toward the longer end.

Why a block heater timer saves you money

A block heater runs on electricity the whole time it is plugged in. If you plug in at 6 PM and leave at 7 AM, most of those hours do nothing for you.

A timer fixes that. You plug the car in at night, and the timer turns the power on a few hours before you leave. NRCan suggests this to save money. CAA-Quebec gives the same tip to cut your electricity bill.

The City of Saskatoon made a short video on this. It says to set the timer to turn on two hours before you need to drive.

Photo: SeppVei, CC0, via Wikimedia Commons

Does a block heater really save gas?

Yes, and the numbers come from official sources.

• NRCan says that at -20°C, a block heater can improve overall fuel economy by as much as 10%.
• NRCan says that on a single short trip at -25°C, the savings could be around 25%.
• CAA-Quebec says a plugged in car can use up to 15% less fuel, and more on trips under 20 km.

Short trips in the cold are where you burn the most extra fuel. Our guide on winter fuel and EV consumption in cold weather explains why.

Block heater extension cord safety in winter

This is the part people skip, and it is the part that can start a fire. Ontario's Electrical Safety Authority (ESA) gives clear rules for outdoor cords:

• Use an extension cord rated for outdoor use. ESA says an indoor cord used outside could cause shock or fire.
• Use a grounded cord with three prongs. Never remove the ground pin.
• Plug into an outlet with a GFCI. If your outlet does not have one, ESA says you can buy a portable GFCI adapter.
• Do not run a cord through a door or window.
• Do not join several extension cords together.
• Check your cords before you use them.

The Saskatoon Fire Department adds a few more tips:

• Check the block heater cord and the extension cord for cracks or frayed spots.
• Keep the cap on the block heater plug when you are not using it.
• Never drive over the extension cord.
• If you drive away while still plugged in, check the cord, the plug and the outlet for damage before you use them again.

My own habit is simple. I hang the extension cord over the side mirror. I cannot drive away without seeing it.

How much a block heater costs in Canada

Many new cars sold in Canada already have one. CAA-Quebec says many automakers install block heaters on the assembly line, so check before you buy one.

If your car does not have one, CAA-Quebec gives these numbers:

• Part only: about $50 to $200
• Installation: about $100 to $250 or more

The price depends on the model, the type of heater and the shop. CAA-Quebec also says a block heater that is put in the right way will not damage your engine. Have it installed by a certified mechanic or follow the maker's instructions.

Block heater or remote starter: which one does what?

People mix these up all the time.

• Block heater: warms the engine block and fluids.
• Remote starter: runs the engine to warm the cabin. CAA-Quebec says it warms the cabin but not the engine or its parts.

Idling is not a good way to warm up a car. NRCan says that in most cases you need no more than 60 seconds of idling after a cold start in winter. Driving at a moderate speed for a few minutes is the best way to warm the engine and the cabin. CAA-Quebec gives the same advice: drive gently instead of idling.

Our article on warming up your car in winter, idling bylaws and remote starters is coming soon.

If your car still will not start in the cold

CAA-Quebec has a simple rule:

1. Check your owner's manual for the cold start steps for your car.
2. Try for no more than 8 to 10 seconds at a time.
3. Wait about 30 seconds between tries.
4. After three or four failed tries, call roadside help.

Often the real problem is the battery. CAA-Quebec says that at -30°C, a car battery keeps only about 25% of its starting power. It also says a battery often lasts around four years. Have yours tested before the deep cold. Our full guide to car batteries in extreme cold is coming soon.

The right engine oil helps too. See our engine oil before winter guide.

What about electric cars and plug in hybrids?

An EV has no engine block to warm. The idea is the same, though. CAA-Quebec says to schedule cabin preheating while the car is still plugged in. This helps keep your range and clears the windows before you go.

For the numbers on range, read our guide on how much EV range you lose in winter.

My quick block heater checklist for this winter

• Find your block heater plug. It is often tucked behind the grille.
• Check the plug, the cord and the cap for damage.
• Buy an outdoor rated, three prong extension cord and a block heater timer.
• Make sure your outlet has a GFCI.
• Set the timer for two to four hours before you leave.
• Plug in below -5°C, and every time at -15°C or colder.
• Unplug before you move the car.

For the rest of your winter prep, see our polar vortex car winter prep guide and our winter tire laws by province.

FAQ

At what temperature should I plug in my car in Canada?

CAA-Quebec says to plug in your block heater once it drops below -5°C. It strongly recommends it at -15°C or colder. If your owner's manual gives a different temperature, follow the manual for your car.

How long should a block heater be plugged in before I drive?

NRCan says a timer that turns on two hours before you drive is usually enough. CAA-Quebec says three to four hours. You do not need to leave it on all night.

Is it bad to leave a block heater plugged in all night?

It mostly wastes electricity. NRCan and CAA-Quebec both suggest a timer instead, so the heater only runs for the few hours before you leave.

Can I use any extension cord for my block heater?

No. Ontario's Electrical Safety Authority says to use a grounded, three prong cord rated for outdoor use, plugged into a GFCI outlet. Never use an indoor cord outside, and do not join cords together.

Does a remote starter do the same job as a block heater?

No. CAA-Quebec says a remote starter warms the cabin, while a block heater warms the engine and its fluids. NRCan also says you rarely need more than 60 seconds of idling after a cold start.