Bunk LedgerCold-weather cab gear and block heaters (2026)
A prairie or northern route at about −30 °C is a different problem from a damp night near freezing. Clothing and glass still matter, and so does whether the engine will turn over in the morning. This note is for US and Canadian drivers who already have a sleeper. It is not a winter test, and it does not name a wattage we measured.
The companion list for blankets, moisture tubs, and 12 V throws is winter cab gear. Shore plugs are in the shore power note. Inverter limits are in the inverter guide.
What the cold is asking the cab to do
On a phone, this table moves sideways. The first column stays put.
| Job | What to look for | Cab note | Not for |
|---|---|---|---|
| Start a cold engine | A block heater or coolant heater made for that engine, with the watts printed on it | Shore power is the usual feed. Confirm the truck manual before you add one | Guessing a universal wattage, or running it all night from a starting battery through an inverter |
| Keep a person warm while parked | A 12 V heated throw with a fuse, or the truck's own bunk heat | One load on the fuse. It is a blanket, not an idle policy | A 120 V household blanket, or any heater that burns fuel in the sleeper |
| Hands and glass | A long scraper and a dry spare pair of gloves | The glass on a tractor is taller than a car's | A cotton layer that stays wet after one yard check |
| Moisture | A lidded moisture absorber on the floor | Cap it before you roll | A tub that can tip into the aisle |
Block heaters and the inverter
A block heater is an electric element in or against the engine, fed by a cord. The photograph further down is a heater for a Honda car engine. It shows the idea of a corded element. It is not a truck part, and it is not a size we are telling you to buy. The truck manual, or the heater made for that engine, is the source for fitment.
Read the watts on the label of the heater you actually have. Do not take a wattage from this page. A heater that sits near the top of a 1,500 W inverter's continuous rating is a poor overnight plan on a starting battery. The inverter has to be rated for the continuous load, the cables have to match the inverter sheet, and the battery still has to crank the truck in the morning. Shore power is the usual way these heaters are fed.
Shore plugs are not interchangeable. A household 15 A plug, a TT-30, and a 50 A campground plug are different inlets. Do not backfeed an inverter into the shore inlet. Do not coil a loaded cord under a blanket. Company trucks often forbid drilling and hardwiring. If the carrier forbids an added heater, the carrier's rule wins.
An unvented propane or butane heater does not belong in the sleeper at any temperature. A cracked window is not a carbon-monoxide plan.
What to carry when the forecast is severe
Keep a dry layer that is not the shirt you drove in: a knit cap, wool or synthetic socks, and a spare pair of gloves. Cotton next to skin stays wet if you sweat a load. A scraper you can use from the ground beats a short one that makes you climb icy steps.
If the truck has an APU or a factory bunk heater, learn that system before you add a household heater. Idling rules are a company and a local question. Follow the carrier's idle policy and the local rule.
On the road
An ice road is a seasonal operation with its own rules. The picture is not a suggestion to drive one. It is a reminder that Canadian cold is not the same as a frosty morning on a southern interstate.
Conclusion
Dress for the person and plug the engine heater into the power source it was built for. The inverter is the wrong overnight supply for a heater that already asks for as much continuous power as a large inverter can give.
FAQ
What wattage of block heater should I buy?
The one printed for your engine. This page does not have a universal number. Read the label and the truck manual.
Can I run the block heater from the inverter all night?
Plan on shore power. A heater near the top of a 1,500 W continuous rating is a bad overnight load on a starting battery.
Is −30 °C a different gear list from a freeze?
The same safety rules apply. You will care more about a dry spare layer, a scraper, and a heater that matches the engine. We have not measured a cab at that temperature.