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How Long Can I Run my Truck’s APU?

Adding an auxiliary power unit, or APU, to your truck is quite an investment. These products can range from five-thousand dollars all the way up to twelve-thousand dollars. What they offer though is worth it. When your truck has an APU installed you will have a source for power, heating, and air conditioning all without having to idle your trucks’ engine. This ends up saving you money on fuel and maintenance as well as keeping you in compliance with anti-idling laws.

Over the past few weeks I have been looking at and answering the most common APU questions. My goal here is to provide a one stop place for all APU related questions. Today’s topic is going to focus on just how long these APUs will last? How long will they run before they need to rest? Knowing this number can be an important factor when it comes to purchasing an APU.

How Long Can They Run?

Before I can answer this question we first have to determine if the APU you are looking at is electric or diesel. Answering this question can have a significant impact on how long your APU will last.

Electric APUs

An electric APU does not run off of an engine but instead pulls its power from batteries. These batteries are charged as your truck’s engine is on either while driving or idling. Then, when you are done for the day or are at a period where you no longer need the truck’s engine you can flip the APU on to begin enjoying the stored power.

Because electric APUs use stored power that means that there is a time limit involved. The batteries can only store so much power before they are depleted. Even the longest lasting electric APU on the marketplace, Thermo King or Carrier Comfort Pro, can only last between ten to eleven hours. That eleven hour timeline is in flux as well and it can vary depending on the variables that are introduced. For example, if you are driving in Phoenix in August and are facing one-hundred degree temperatures then your electric APU will NOT last that full eleven hours. The air conditioner is going to be running constantly trying to keep up which will result in more power used.

The same can be said if you are driving up north in Maine or North Dakota in the dead of winter. More power will be consumed just to keep your cab warm. This will result in a shorter battery life. Along with the weather you also need to consider if you will be running other electronics or appliances along with your air conditioner or furnace. That eleven hour timeline is based on ideal conditions and ONLY using the air conditioner or the furnace. If you add more electronics/appliances then you will be draining more power which will result in a shorter timeline.

In short folks an electric APU will most likely not get you through a solid night of rest. Chances are you will run out of battery charge sometime throughout the night. When the batteries have run out of charge it will take anywhere between four to eight hours of your truck’s engine running to charge the batteries back to full capacity. These electric systems are recommended for folks who will be waiting at a dock or a port for a few hours at a time. These are not the recommended systems for long-haul drivers.

Diesel APUs

Now that we have the electric systems covered it is now time to take a look at the diesel systems and exactly how long they can last. As I mentioned earlier, diesel systems are by far the most popular type of APU. They are much more reliable, provide more power, and can power for a much longer period of time. Their main downside is that they do use diesel fuel and they are not the most environmentally friendly. (It is more friendly then idling your engine, but you are still running a diesel engine.)

Most diesel APUs will be connected directly to your truck’s fuel tank. A trucks’ fuel tank can typically range anywhere from one-hundred and twenty-five gallon to three-hundred  gallons. Now, typically when idling you burn anywhere from 0.75 to 1.25 gallons per hour. As you can imagine, this can add up fast when idling for a long period of time. A diesel APU though will only eat between 0.10 to 0.50 gallons per hour. If we take the average between both numbers we get an 1.00 gallon per hour use when idling and a 0.25 when using an APU. As you can see, that is a significant difference in fuel spent.

Now to answer your question as to how long a diesel APU will last. So, let’s use a 125 gallon tank as an example and a burn rate of 0.25 gallons per hour and also assume that your fuel tank has 60 gallons of fuel in it. In this scenario you could run your APU for over two-hundred hours without having to refill your fuel tank. Obviously, this is an extreme example but it gets the point across of why diesel APUs are so popular. When taken care of and proper maintenance is done these APUs can provide you with endless hours of power, heating, and cooling while on the road.


In conclusion folks the amount of time your APU can last depends on quite a bit of variables. Is your APU electric or diesel? If it is electric what is the rated time? What climate are you in? There are a lot of factors that can contribute to how long an electric APU can last. If you have a diesel model then how much fuel do you have left in the tank? How long do you plan to run it because chances are your diesel APU will last much longer then you actually need it. The only thing I can say is make sure you have enough diesel in your tank before you decide to run the APU all night. Besides that, you’ll be fine.

Thanks for reading,

Alec Johnson

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