How many hours does a semi truck spend idling?

Answer 1

Hard to say. If you've got an old engine and it's cold outside, you might idle all night. Electronic engines (ones with electronic fuel injection) have thermostatic idle control. Cummins calls theirs Icon Idle, Detroit Diesel calls theirs Optimized Idle and Cat has one but I don't know what it's called. With this system you plug in the temperature you want your cab to stay at and it starts and stops the engine as needed to maintain it. You might idle three hours per night (to a trucker, "night" is ten hours) with this system.

The real deal is to have an auxiliary power unit on your truck--if you have a new truck, you've probably got one. With those you don't idle the main engine at all; the APU runs the heat and AC.