What is the purpose of having BOTH a bunk heater and an APU?

Bunk heaters are almost standard on trucks, but adding the AC is why I'd want a standalone APU. My truck has the electric APU, and auto idle.

 

The reason is efficiency, in VERY cold, the apu will idle up to keep batteries fresh and engine warm,

The bunk heat is integrated with the ac ducting for warmth but the electric current draw for fan and ignition element on the heater would be too great over a long period of time, if running the apu and using the coolant for a heater core, it will also not be quite warm enough to keep the cab quite warm enough even as it raises engine temp enough to keep it from freezing in extreme temperatures.

 

The bunk heater is a enclosed space heater that has a higher efficienct rating over an apu. Tho it will in time draw down the batteries. Not all companies will supply you with an APU. Tho they will supply you a bunk heater.

APU's keep you comfortable in the heat and use a pint per hour of fuel. Where if you have to idle your truck you will guzzle 1 gallon per hour to keep your sleeping area cool in the summer.

Bunk heaters are about $50-$100
APU are around $800-$2000

 

Are you talking about a webasto bunk heater along with an apu?

 

I think you mean $8K - $12K.

 

Scratch that, I'm speaking to a diesel powered APU.

 

Some APU’S use a bunker for heat . If it’s a separate bunk heater it’s great for a quiet sleep in moderate temperatures and is cheaper to run than a APU plus it saves on APU hours which lowers APU maintenance.

 

A bunk heater is part of the APU.