Trucks at Work
APUs and you

APUs and you

The use of idling reduction technology could reduce the fuel consumption of a long-haul tractor by some 1,900 gallons or 7,200 liters per year, which equates to an emissions reduction of greenhouse gases of some 42,000 lbs or 19 metric tons.” –David Bradley, CEO of the Canadian Trucking Alliance (CTA), in a speech three years ago calling for tax credits to help spur wider investment by truckers in auxiliary power units (APUs).

There’s a lot of debate about the value of auxiliary power units (APU) these days.

One the one hand are two studies – one conducted by the NC Solar Center (NCSC) at North Carolina State University back in 2007 and another by the American Transportation Research Institute (ATRI) in 2009 – that show the return on investment (ROI) in an APU can take longer than expected; so much so that in some cases the studies found it might not be worth investing in an APU at all.


Without specifying technologies, ATRI found in its research last year that APU payback time periods ranged from 16 to 45 months for some units, while others “were not expected to provide a payback within the period of ownership.” It also pointed out that its ROI findings were based on “the level of baseline idling, the usage of the technology, and the start-up and ongoing costs.”

The three-year NCSC project drew its conclusions from 20 trucks that operated for over 2.8-million miles in 42 states and concluded that, using the demonstration field test as a specific sample, APUs require at least a five-year payback period when fuel costs are $4.50/gal or less. The authors noted that as base engine emission standards become more stringent, the emissions benefit of APUs will drop, although fuel use and carbon dioxide (CO2) reduction benefits will remain unchanged.

On the other hand, however, is a simple formula given to me by our contributing editor Tim Brady – a former owner-operator with over two decades of experience who always spec’d his trucks with diesel-powered APUs.

“It’s very basic,” he told me. “At idle, you measure truck engine fuel consumption in gallons per hour per hour. For diesel-powered APUs, you measure fuel consumption in pints per hour. Now, you go do the math.”

As there are eight pints in a gallon, that put the fuel-saving advantages of just diesel-powered APUs in pretty clear perspective. And when diesel fuel shot up to over $5 a gallon just a few short years ago, that simple formula Brady shared with me took on much greater importance.


Still, APUs can be fairly pricey. One reason the American Trucking Associations (ATA) and Canadian Trucking Alliance (CTA) jointly called for more government tax support for APUs revolved largely around their price tag – ranging anywhere from $6,000 to $10,000 in the U.S., with an average of $7,750, which includes installation costs as well as cost of operation.

Also, APUs themselves have undergone tremendous change in just the last few years, with a wide variety of new models coming to the fore powered by electricity, diesel-fuel, even hydrogen. Making a choice on the type of technology, as well as initial price and life-cycle cost, adds to the complexity truckers must navigate through.

For some insight into the technology aspect of APUs, I sent some questions to Garfield Walker, product manager for mobile valves at Parker Fluid Control Division located in New Britain, CT; a firm specializing in APUs.

Garfield, who’s been this division for 12 years, specializes in automotive, commercial and industrial equipment. Here are some of his thoughts on the matter, to help inform your own decision on the subject of APUs.

First, what kinds of APUs for long haul truckers are available today? What are the pros and cons of these designs?

Walker: There are a variety of battery-based and diesel-fuel APU designs available on the market today. Both battery-based and diesel-fuel designs provide adequate electrical power for heating, cooling and truck cab electrical devices. However, a few differences between the two systems might make one more attractive than the other, depending on the driver’s priorities.


The intrinsic design of the battery-based APU funnels power from the vehicle’s electrical system to the batteries – avoiding the need for fuel. As a result, this design features 100% savings on fuel costs while diesel APUs only offer reduced fuel savings. Additionally, battery-based designs require little maintenance while diesel APUs need regularly scheduled maintenance to ensure smooth operation.

With zero emissions, battery-based designs ensure compliance with all of the states’ no idling laws. Diesel APUs produce low emissions, also meeting states’ no idling restrictions. As another bonus, battery-based APUs generate little noise during operation, which helps drivers meet multiple states’ noise ordinance laws as well.

Although battery-based designs appear to have a clear advantage over diesel APUs, there are a few drawbacks to this design. The first is limited battery life – typically four years. Second, it takes roughly four to six hours to recharge the battery. Third, once powered up, the battery-based design offers limited system run times.

What new APU designs are becoming available for truckers to use?

Walker: Currently, the market is comprised of mostly diesel APUs; however, battery-based systems are gaining in popularity. In three to five years, though, we are going to see hydrogen fuel cells, which may rival those two systems to become the trucking industry’s most popular APU system.

What do manufacturers hope to achieve with new APU designs? Be able to plug them in at truck stops?

Walker: When designing new APUs, manufacturers focus on increasing systems efficiency and reducing maintenance requirements. OEMs carry weight in these design decisions as well. OEMs committed to diesel APU designs want to utilize less fuel to achieve the desired performance. OEMs dedicated to battery-based designs hope to achieve shorter recharge times, and increased capacity and battery life. As for the question of plug-in APUs at truck stops, a greater infrastructure needs to be present to attract fleet and personal truck owners to pursue this as a cost-effective option.

What do you think the best design for the future will be?

Walker: A battery-based system may prove the best design choice for the future due to low maintenance, superior fuel savings and 100% emissions compliance.