What is the Best Truck Auxiliary Power Unit (APU)?

For those of you who have been in the trucking game for quite a while you know the benefits of having an auxiliary power unit on your truck. This holds especially true for those long-haul drivers who are on the road for multiple nights each week. An APU allows you to heat, cool, and provide power to anything else you desire all while without having your truck idle. Idling your truck is not only wastes fuel but it can also increase maintenance needs on your engine and even on your diesel particulate filter (DPF).

Constant idling can lead to costly repairs that may have not shown up for years down the road. If you couple that with the fact that many states do not allow idling for a long period of time then you are left with two options to get a comfortable sleep during winter or summer. The first is finding a hotel room for each and every night. This gets old and can get expensive fast. The other option is getting yourself an auxiliary power unit, or APU.

Purchasing an APU for your truck or for your fleet can be a daunting task though. There are a lot of brands out there today and each one is different. In this article we are going to take an in-depth look at the best of the best when it comes to APUs. I will tell you right now that if you are looking for a budget build then this is NOT it. The APUs in this article are top of the line and will be the most expensive.


Now before I get into what APUs are the best I first want to go over a few considerations that I looked at before writing this article. A lot of folks can say that brand XYZ is the best but how did they come up with that? Is it just a feeling, or is there factual information behind it? I am and have always been a facts and numbers guy. I need to see the proof and understand the proof before I believe that something is the best. Because of that I want to illustrate the specific considerations that I looked at when selecting these two best APU models for your trick.

Diesel Versus Electric

There are two main types of APUs out there today: Diesel and Electric. The most common is the diesel model but electric has its uses as well. In order to identify which model is correct for you we need to determine if you are spending nights on the road and need power for multiple hours at a time. Or, if you are a day driver and may end up spending an hour or two waiting at a dock or port.

First, let’s look at the waiting at port or dock scenario. You do not want to be idling this entire time but you also do not need an entire diesel engine just to provide you with heating/cooling for an hour or two. Chances are you are also driving a cab with no sleeper so there is less room to heat and cool. In this example an electric APU would fit perfectly for your needs. However, if you are a long-haul driver, have hit your hours for the day, and will be needing power for ten or twelve hours… then you will most definitely need a diesel APU.

While electric APUs are cleaner and produce no noise they are also limited. These APUs draw power directly from your vehicle’s batteries. When the power is drained from your batteries you have no APU power. Along with this the batteries can only produce so much power at one time. So, if you have a high capacity air conditioner and wish to run a television and a microwave then the electric option is not going to be for you.

But, if you’re just looking to stay cool while waiting at the port of Los Angeles for an hour or two then electric may be the best option for you. The one thing I can say here is that electric is NOT a one size fits all approach whereas the diesel is. The diesel APU will work while waiting at port and it will work during overnight trips. The electric will ONLY work at port or dock. Keep this in mind when selecting your APU type.

Maintenance Needs

APUs are engines with moving parts and will require maintenance. That is just a fact of life. How much maintenance your APU needs can be a big deciding factor when it comes to purchasing a unit. Depending on the brand of APU you go with you could be looking at maintenance needs every one-hundred hours of use, five-hundred hours, one-thousand hours, or even two-thousand hours. (One point of note here is that if you do decide to go with an electric APU rather then diesel you will see a significant savings in maintenance needs.)

Now, while every one-hundred hours of use does not sound that bad keep in mind that if you are doing overnight trips for our five days a week for ten hours or more each night then you could be looking at fifty hours of use just after one week! This could mean maintenance on the APU once a month or even twice a month. This is not a hassle free system and requires your involvement just to keep it running correctly. This is why that model with the two-thousand hour maintenance needs is so attractive. Using the same scenario above where a driver is using the APU for forty to fifty hours a week you will now only need maintenance once, maybe twice, a year. The rest of the year you are good to rely on  your APU.

The last point to mention when it comes to maintenance and APUs is finding replacement parts and technicians who are experienced with the APUs. If you buy a lower cost APU from a lesser known brand then you are going to have trouble finding parts and mechanics who are familiar with the brand name. However, if you purchase an APU from a recognized name then you will be able to find parts that much faster and most techs will have already seen them before and know exactly how to work on them.

Wattage Capacity & Run Time

The last consideration to review before we move on to our best APU brands is the overall wattage that they can produce and their run time. Now in most cases a diesel APU is tied directly into your existing diesel fuel tank. So, the run time is tied directly to how much fuel you have left. If you have an electric APU then your run time is directly impacted by how much life your batteries have left in them. Do note that when you start your truck engine up again the batteries will automatically begin to recharge… but it can take six hours or more for them to fully recharge. If you have a diesel then run time is not much of an issue as long as you have a reasonably full fuel tank.

A diesel APU is more or less a portable generator that goes with your truck. The engine on the APU produces kinetic force which feeds into the alternator causing rotation and resulting in electrical current being generated. As far as how much current or wattage is being generated that depends on your APU. If the APU is on the lower end of the pricing scale then the wattage it produces will most likely be lower as well. This could mean that you are stuck with only using heating or air conditioning and are not able to power a television or microwave as well.

On the other hand, if you purchase a higher end model then the wattage will be increased as well. This means more power! (I’m reminded of the old Home Improvement show with Tim Allen.) More power generated means that you are able to run more appliances and electronics off of your vehicle’s APU. If you are just looking for air conditioning/heating and nothing more then this may not be a concern, but if you want some other creature comforts then definitely consider the wattage output of the APU.

The Best APUs

Alright folks we are now on to the bread and butter of this article. You understand my logic and considerations from the above points. I also want to make it known that I asked various truckers across the country what their thoughts were on the best APU unit. As I had expected their feedback matched my research as well. In essence there are two main brands when it comes to wanting the best APUs for your truck. Let’s take a look:

Thermo King

Thermo King truly is the king when it comes to auxiliary power units. They have been the reigning company on APUs for many years and are still sitting on top as I write this article towards the end of 2020. When I had reached out to various truckers the constant feedback was that Thermo King was the best. Many folks could not afford them because of their very high price point but there seemed to be no debate that Thermo King was the best of the best. Their home page on their APU products can be found by clicking here.

Now earlier I had mentioned the whole diesel versus electric debate and which one would be the best for you. Well, Thermo King has both options for you to choose from. Their diesel model is known as Thermo King TriPac. The official brochure for this APU can be found by clicking here. This diesel APU can run for two-thousand hours without requiring maintenance. This is the top tier as you will only need to maintenance it a few times a year. If something does go wrong with the TriPac unit there are hundreds of certified dealers spreads out across the country that can diagnose and repair the system.

For those of you that want to go with the electric route Thermo King has their Envidia all electric APU model as well. The official brochure for this APU can be found by clicking here. This model boasts having the longest running electric APU within the industry at ten to eleven hours. Note, that run times are extremely variable depending on if you have multiple appliances or electronics running or if you are in a harsh environment like Phoenix, Arizona in August or Bangor, Maine in January. Once the battery has been depleted it will take anywhere from four to eight hours for them to be recharged.

Both of these products can provide you enough power to heat and cool your cab comfortably as well as power accessory appliances or electronics such as a refrigerator, television, computer, or microwave. There are many add-on options as well that Thermo King offers such as adding a one-thousand watt power inverter or adding the option for a shore power converter. Overall, you cannot go wrong when it comes to a Thermo King unit… just be aware that they can be quite expensive. If you are unable to afford it out right you could either look at financing or also look at some of the refurbished models that are out there.


The second best model worth bringing up here are the diesel and electric models from Carrier. These ‘Comfort Pro’ models are a very close runner up when being compared to Thermo King. There were many reefer drivers that swear by Carrier’s APUs over Thermo King. At this point it seems too close to call on exactly which one is better. I only put Thermo King at the top as I had more folks recommend that… but those that did recommend Carrier were quite fanatical about it. So, who truly knows?

Carrier’s diesel APU option can be found by clicking here. Just like the Thermo King unit this diesel APU Comfort Pro can go as long as two-thousand hours without needing maintenance. While Carrier does not have as many dealers as Thermo King does they are adequately spread-out across the country so that you can find a repair shop at each major city you drive through. I used to work for a dealer group that owned a few Carrier-Transicold shops and we had one in Kansas City and then another in Colombia, Missouri which was only about 70 miles away. The point being is you should be able to find one without any issues.

Carrier also has their electric APU unit which can be found by clicking here. Again, just like Thermo King this unit comes with a ten to eleven hour run time. I do find it a bit funny that Thermo King states they have the longest running electric APU and then here is Carrier offering a unit with the same run time. I could not find the average charge time on these batteries but since we have about the same run time as Thermo King I am going to assume we would still be looking at around four to eight hours.


Alright folks so there you have it. Thermo King and Carrier have the absolute best APUs on the marketplace today. Yes, there are many other brands out there from various manufacturers such as Centramatic, Kubota, Kohler, Cummins, Dynasys , Rigmaster, and Green APU but when it comes to ranking them Thermo King and Carrier are truly the best of the best. I do not want to diminish some of these other brands though. If I had to choose something other then Carrier or Thermo King I would most likely go with a model from Dynasys or Green APU.

Dynasys is a cheaper model and requires maintenance every one-thousand hours. Green APU is a similar story and requires maintenance every six-hundred hours. So, while you’re not getting that two-thousand hour benefit you are still saving a significant amount of time when compared to the one-hundred hour maintenance units.

All in all though folks, the decision is ultimately up to you. Do you want to spend that extra money and get a premium APU? Or, do you want to save some money and get a product that sits right in the middle? Or, are you strapped for cash and are looking at that one-hundred hour system? The choice is yours.

Thanks for reading,

Alec Johnson


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