‘We used to manage MPG, but now we also manage idle time.”
A large US fleet
Diesel APUs allow fleets to meet the temperature and electrical power needs of their drivers. They provide a complete solution to the reasons many fleets idle, but are more expensive to install and maintain than other systems and they consume diesel fuel.
With diesel APUs, an auxiliary power unit powered by the diesel fuel already on the tractor can provide power for HVAC, hotel, or other electrical loads while the vehicle is parked. Some units provide all three needs while some provide cooling and AC power but require adding a fuel-fired heart for cab heat. Diesel APUs also charge the vehicle’s batteries. They burn between 0.1 and 0.5 gallons of fuel per hour. Diesel APUs provide AC power either through a generator or using an inverter.
Diesel APUs provide a complete solution for heating, cooling, and AC power.
Diesel APUs are well-suited for operations in extreme hot or cold temperatures
They provide almost unlimited time for heating, cooling, and AC power.
Diesel APUs are more expensive to purchase, install, and maintain than other idle-reduction solutions
They require periodic oil and filter changes
While they reduce fuel use from idling, diesel APUs still consume fuel
Some areas restrict the use of diesel APUs
Diesel APUs are one of the possible anchor technologies for an overall idle-reduction strategy:
Executives from 11 for-hire truckload carriers were personally interviewed to find out about their idle-reduction practices. No single technology was used by all 11 of the fleets, but diesel APUs were among the least common strategies used by these fleets.
However, one fleet executive said, “APUs win for reducing idle time the most.”
Internet Fleet Survey
In conjunction with Michelin, the study team surveyed 200+ members of Michelin’s Fleet Forum. When asked what idle-reduction technology they would purchase 33% said diesel APUs. Survey respondents said diesel APUs and fuel-operated air heaters were the most beneficial idle-reduction technology.
Here are comments from some of the respondents:
- Purchased 15 years ago, was best all-around choice
- We experienced as much as three-quarters additional mpg by adding APUs
- Diesel APUs do everything
Internet Owner-Operator Survey
In conjunction with Kevin Rutherford’s “Let’s Talk” truckers’ satellite radio forum, the study team surveyed owner-operators and small fleets. A large number indicated they would spec diesel APUs on new trucks they purchased. When asked why they chose diesel APUs for idle reduction, here is what some of them said:
- It takes care of all the same things that are provided by the truck engine.
- It is the technology that is most portable. I can use it at pickup/delivery areas, rest areas, and customer parking lots.
- I can sleep in the truck in full sun in south Texas in 100+ degree temperatures.
There are already a wide variety of payback calculators for any given type of idle-reduction system. In an effort to meet the industry’s need for more information, we have also developed a high-level payback equation to aid fleets in choosing the right combination of technologies.
Only one truck manufacturer offers a diesel APU as a factory-installed option, but others have an option that provides a mounting location and some of the connections to enable faster and easier installation of a diesel APU. Manufacturers agree that a diesel APU should be ordered with an inverter.
Diesel APUs address many of the reasons fleets cite for idling including heating, cooling and AC power. They can operate in extreme temperature conditions and have almost limitless hours of operation — they’ll run as long as there is diesel fuel available. However, since they run off diesel fuel they generate emissions and noise, and they require maintenance on a regular basis.