Auxiliary power units have an additional advantage over both the coolant and interior heaters in that:

Question

Quizplus · Accepted Answer

Auxiliary power units can produce electrical power for appliances and accessories, which is an advantage over coolant and interior heaters. They also use less fuel than idling the truck's engine, but this is not necessarily an advantage over the other two options listed. While they may be able to heat the air in the cab or sleeper, this is not their primary function. Keeping the engine warm for easy starting is also a function of the coolant heater, not the auxiliary power unit.

Auxiliary Power Units Have an Additional Advantage Over Both the Coolant