Block Heater Timers
The single biggest block heater mistake in Canada isn't buying the wrong heater — it's leaving the right one plugged in all night. An engine reaches its maximum pre-heat in about four hours; the other eight hours on the cord are pure waste. A $20 outdoor timer fixes that permanently, and usually pays for itself inside a month of prairie winter.
Run the numbers for your own heater and province with the electricity cost calculator, and check tonight's forecast with Should I plug in tonight?
Mechanical vs digital vs Wi-Fi
| Type | Price | Strengths | Cold-weather gotchas |
|---|---|---|---|
| Mechanical dial | $10–$20 | No programming to lose, no electronics to fail, handles 15 A resistive loads all day | Dial and gears stiffen in extreme cold; a power outage shifts the whole schedule; 15–30 min setting increments |
| Digital | $20–$35 | Exact on/off times, separate weekday/weekend programs, some keep time through outages | Cheap units lose their program in an outage or shut down below -30 °C — check the rated operating temperature and battery backup |
| Smart / Wi-Fi plug | $25–$50 | Turn the heater on from bed when a cold snap surprises you; pair with routines or weather automations; energy monitoring on some models | Needs 2.4 GHz Wi-Fi reach to the driveway; must be an outdoor (wet-rated) model with a cold operating range; useless during an internet outage unless it has offline schedules |
Mechanical dial: The default. Buy the heavy-duty outdoor version, not the lamp timer.
Digital: Worth it if your schedule changes day to day.
Smart / Wi-Fi plug: The most flexible — if your Wi-Fi reaches the parking spot.
The amperage check
A block heater is a continuous resistive load, which is exactly what cheap lamp timers aren't built for. Match the timer's resistiverating (not the motor or tungsten rating) to your heater's draw:
| Heater wattage | Draw @ 120 V | Typical application |
|---|---|---|
| 400 W | 3.3 A | Cartridge and small frost-plug heaters (most cars, small SUVs) |
| 750 W | 6.3 A | Mid-size frost-plug heaters, circulating heaters |
| 1,000 W | 8.3 A | Full-size truck and diesel frost-plug heaters |
| 1,500 W | 12.5 A | Large circulating heaters, heater + battery blanket combos |
Your vehicle's heater wattage is on its vehicle page where the catalog lists it, or in the wattage guide. If the timer also feeds a battery blanket or oil pan pad, add the wattages together before checking the rating.
Setting it up right
Set the ON time 3–4 hours before your usual departure and skip the OFF programming — just unplug when you leave. Mount the timer at the outlet, not at the bumper, so the connection under snow is a plain cord joint rather than an electronics box. And plug the timer directly into the wall: timer, then extension cord, then heater. A timer dangling at the end of 50 feet of cord in a snowbank is how water gets into the contacts.
If the breaker trips when the timer clicks on, that's almost never the timer — see why block heaters trip breakers.
Our picks on Amazon.ca
Every pick is outdoor-rated with a 15 A / 1,875 W resistive rating — enough for any consumer block heater, including heater + battery blanket combos.
BN-LINK 24-hour mechanical outdoor timer
The classic dial timer in an outdoor-rated case, 15 A resistive. Nothing to program, nothing to reset — set the pins for 3–4 hours before departure and forget it.
~$18 on Amazon.ca →
BN-LINK 7-day digital outdoor timer, 2 outlets
Separate weekday/weekend programs and exact on/off times, rated 15 A / 1,875 W. Two grounded outlets — block heater on one, battery blanket on the other.
~$26 on Amazon.ca →
Kasa KP401 outdoor smart plug (Wi-Fi)
Turn the heater on from bed when a cold snap surprises you. IP64 outdoor housing, runs on 2.4 GHz Wi-Fi, and schedules keep running if the internet drops.
~$20 on Amazon.ca →
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and change often — check the listing.
FAQ
How long before driving should the timer turn the block heater on?
Two to four hours. Block heaters reach their maximum coolant temperature gain in about 4 hours — everything after that is wasted electricity. At -15 °C, 2 hours is plenty; at -30 °C and colder, use the full 4 hours. Set the timer to switch on 3–4 hours before your normal departure.
How much money does a block heater timer save?
Roughly two-thirds of your plug-in cost. A 1,000 W heater left plugged in for 12 hours uses 12 kWh — about $1.20–$2.40 a night depending on your province. On a timer running 4 hours, that drops to $0.40–$0.80. Over a 150-night prairie winter, that's $120–$240 saved from a $20 timer.
Can I use an indoor timer outside for a block heater?
No. Indoor timers aren't sealed against snow and meltwater, and their contacts and cases aren't rated for a 1,000 W continuous load at -30 °C. Use a CSA-certified outdoor timer rated 15 A resistive, with a cover that closes over the plug.
Will a timer handle a 1,500 W block heater?
Check the resistive rating on the package — a 1,500 W heater draws 12.5 A at 120 V, which is within a 15 A rating but too much for the 8–10 A lamp timers sold for Christmas lights. Heavy-duty outdoor timers rated 15 A / 1,875 W handle any consumer block heater.
Do timers work at -40?
Good ones do — that's the spec to check. Mechanical timers get stiff but keep working; budget digital units can blank out below about -30 °C. Look for an explicitly stated operating temperature (many Canadian-market Noma and Woods outdoor timers are rated to -40 °C).
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