APUs: The Pros and Cons

16 Nov.,2022


Truck Electric APU

APUs: The Pros and Cons

While developing the SuperTruck, engineers at Cummins and Peterbilt developed a system that used four 3,300-watt/hour lithium-ion (LI) batteries, but they are still not still not cost effective for use as a truck APU. (© Cummins)

Auxiliary power units (APUs) may represent the future of low-emissions trucking, but their merits are still up for debate. True, any trucker with a few overnight trips under their belt will swear by this tech’s ability to actually make rest stops restful by keeping rigs quiet and drivers warm. Nonetheless, the jury’s still out on which APU configurations are the best. Here are some of the factors modern operators and fleet owners consider before upgrading their cabs.

APU Basics

APUs are well-proven technology. In addition to keeping your cab heater running on cold nights without your having to idle the engine, the units play roles in military, municipal, aerospace, and other applications. Of course, your truck probably doesn’t need a NASA-grade APU, but the fact that there are so many varieties and options makes it fairly easy to customize rigs of all shapes and sizes.

The most obvious benefit to installing an APU is fuel economy: Cutting back on idle time means you spend less cash filling up. Some experts estimate that truckers without APUs waste about one percent of their fuel for every ten percent of the time they spend sitting on their hands with the engine humming. For most budget-conscious operators, the question is not whether to upgrade to an APU but, rather, which APU is best.

Tried-and-True Fuel APUs

Diesel APUs are commonly installed in vehicles that continuously need to make long runs, but they have some disadvantages. Regular maintenance is essential to their proper function, and they can be fairly loud. Of course, they’re miles better than idling your engine, and many drivers feel that the frame space they require is a small price to pay for consistent, longer-lasting power.

Some truckers prefer propane-powered units, but they’re less common, so upkeep could be a bit more difficult. These APUs may also lack the ability to warm up the engine block and fuel system before it’s time to hit the road.

Electricity All the Way?

Electric APUs are the latest alternative to diesel and propane. Powered by batteries that recharge when the engine’s running, these devices are usually easier to maintain and less hefty than fuel-driven alternatives, and they are also less noisy. Unfortunately, drivers who routinely make shorter hops may not be able to charge their batteries sufficiently, which could lead to premature power exhaustion. This is especially concerning for truckers whose medical conditions force them to rely on power-hungry devices, like continuous positive air pressure machines.

The other outstanding issue with electric APUs is that the deep-cycle batteries they require to function are less than ideal when it comes to starting up your engine. Furthermore, if your vehicle lacks a high-output alternator that can supply demanding loads, your installation costs may include extra upgrades.

Which APU Is Best?

If you take away one thing from all this, it should be that APUs are still developing technology. Even operators who’ve used them for years say you’re unlikely to find a perfect model to fit every situation you’ll encounter. Regardless whether you’re in a rush to become emissions compliant, you should do a cost-benefit analysis to figure out which APU is right for the driving conditions you typically experience first.

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