The Espar Bunk Heater for Semi Tractor Trailers: A Review

During the early months of 2010, the company truck Mike drove had an Espar bunk heater.

A Review of the Espar Bunk Heater for Semi Tractor TrailersVicki says that she thinks the term “bunk heater” is a little confusing or misleading.

To her, the “bunk” means the bed, not the entire sleeper berth area.

Anyway, a bunk heater is designed to keep the driver warm when it is cold outside but he/she doesn’t want to idle his/her truck.

It’s a designed to save fuel.

Its Design and Location

A photo of the control panel for the Espar bunk heater.This is the control panel of the Espar bunk heater in Mike’s truck.

There are three buttons and a dial.

The button on the top left is for heat and when the heat is on, the red light comes on.

The button on the lower left is for the fan to blow and when it is on, the blue light comes on.

The middle button is to turn the unit off, whether from the heat or fan setting.

The dial on the right allows the user to choose the amount of heat desired.

There is no thermostat to allow an actual temperature setting.

For this reason, it can be a little tricky to set the temperature for running all night.

The control panel of the Espar bunk heater with the air outlet.This photo shows the proximity of the air outlet from the unit under the lower bunk to the control panel.

The control panel was fairly easy to reach when lying on one’s stomach on the lower bunk.

The louvers can be moved up only so far but down pretty far (as shown).

Also, the outlet can be turned left and right a little.

We do not have a picture of the unit under the bunk.

Illustration of Espar bunk heater under lower bunk of Freightliner Cascadia.

However, Vicki has drawn an illustration showing the approximate size of the Espar bunk heater under the lower bunk in a Freightliner Cascadia.

In the truck Mike drove, the unit was installed in the middle compartment on the right hand side (driver’s side).

For drivers who like to store things under their lower bunk, it is a good idea to keep the heater clear of items so that it can operate efficiently.

We must note that we personally never had any problems with anything getting too warm or melting as a result of being too close to the unit under the lower bunk.

Its Operation

According to the manufacturer’s website, “Espar air heaters work as forced air furnaces utilizing the truck’s own diesel fuel and batteries to produce heat.”

This sounds like an ideal solution to keeping one’s truck warm in the winter, especially since supposedly “it draws less than one amp when running and will shut off when desired temperature is reached, then restart when required.”

Our Experience

In our experience, does the Espar bunk heater work as described?

Well, more often than not, it did.

However, we ran the unit one night when the temperature was expected to plummet.

Sometime during the night, the unit turned off, but it never turned back on!

Vicki (who slept on the lower bunk) reached down to turn it back on, but it would not turn on.

It had gotten so cold in the truck that she had to put on more clothes and get back in her sleeping bag just to keep from shivering.

It is possible (although we do not know for sure) that what happened to cause the bunk heater to turn off — and not automatically turn back on — was that the amount of available power in the batteries was so low that it could not turn back on.

(This was before the Arctic Breeze Truck AC was installed in the truck and therefore before new and extra deep-cycle batteries were installed.)

Air Outlet

Since the air outlet’s position can be set only so far, it’s ability to direct the air flow is limited.

The unit we had blew the air straight out toward the sleeper berth’s curtains when the curtains were completely closed behind the driver and passenger seats.

As is also the case with the Arctic Breeze Truck AC, the inability to direct air flow on the Espar bunk heater is a major drawback to climate control in our opinion.

Vicki ended up putting something in the floor to literally direct the air flow up, especially when the fan (not the heater) was turned on to try to help ventilate the entire sleeper berth area (especially the upper bunk, where it was warmer).

The manufacturer’s website says, “Eberspaecher Climate Control Systems manufactures diesel-fired heating systems to provide cab and sleeper heat in trucks, eliminating the need to idle the engine for heat. ….”

However, in our experience, when the sleeper berth’s curtains were closed, only a limited amount of warmth could go up to the rest of the cab.

To overcome this, one can leave the bottom part of the curtains open slightly.

One just has to devise a way to do this.

We could easily envision a driver positioning a small piece of Velcro so that one corner of the sleeper berth curtain would fold back on itself out of the way.

Here is one Velcro product through, with whom we have an affiliate relationship.

Bear in mind the additional resources the heater must use if it has to warm a larger area in truck.

The Lights

The intensity of the blue light that illuminated when the Espar’s fan was turned on greatly disturbed Vicki to the point that she wasn’t able to sleep.

This situation is described in this article by Dr. Joseph Mercola, which opens this way:

There’s growing concern among experts that the proliferation of glowing gadgets like computers may fool your brain into thinking that it’s still daytime after the sun has gone down. Exposure during the night can disturb sleep patterns and exacerbate insomnia.

Dr. Mercola goes on to address in particular “blue light.”

To overcome the Espar unit’s blue light whenever it was on at night, Vicki had to cover it.

Thankfully, it was positioned far enough away from the air outlet that it could be covered fairly easily without inhibiting air flow.

Interestingly enough, the reddish light that came on when the heater was on did not seem to bother Vicki nearly as much as the blue light that came on when the fan was on.

In general, we think that having the lights come on when the unit is turned on is a good thing because the unit runs so quietly that one can easily forget it is on and proceed to start driving without having first turned it off.


As you may have already guessed, this product is not an auxiliary power unit (APU) and does not provide electricity from which the driver may operate other electrically-powered appliances.

If a truck has been designed to shut off power to lights, 12-volt outlets and anything else connected that would pull the charge on the batteries too low for the truck to be cranked, it will conserve its power at that threshold and turn everything else off.

Vicki has experienced numerous times — even without a bunk heater being on — a truck turning off an interior light in the sleeper berth in order to conserve power.

Sometimes if she woke in the middle of the night, she would read or write until she got sleepy enough to go back to sleep.

Still, it must be stressed that the Espar bunk heater is just that, a heater and not a combination unit.

When it had the resources it needed, it worked just fine for us.

truck drivers money saving tip iconMoney saving tip: Being able to stay warm in your truck when it is cold outside without having to idle your truck is good from at least two standpoints:

  • not wearing out your engine prematurely and
  • saving fuel.

It seems that some diesel-powered heaters — like the Espar bunk heater — are dependent upon the charge stored in the batteries.

If you do not have a large enough bank of batteries in your truck or if you have drawn down the power stored in the batteries through the use of other appliances while the truck is turned off, you may not have enough power to keep the bunk heater on throughout your entire rest break.

We would be interested to know how long a bunk heater can keep a truck warm based on starting temperature in the truck.

For example, assuming that the batteries are fully charged in both, would a bunk heater in a truck with a starting temperature of 30°F run longer than one in a truck with a starting temperature of 0°F?

The manufacturer’s website has calculators by which you may calculate (based on your input) your return on investment when you use an Espar instead of idling — after figuring in the cost of the unit

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