Auxiliary power units (APUs) are one of the best tools that you can supply your truck drivers with to combat wasting fuel. The APU makes it possible to power a truck’s heating, air conditioning and other comfort systems without the need to keep the engine idling during rest stops. They help drivers avoid wasting fuel, but they present a different problem because of their weight. With an APU weighing several hundred pounds, they can push a truck hauling its maximum weight limit over the line into non-compliance, depending on where truckers were driving.

Government Recognizing the Benefits

Recognizing the fuel efficiency and environmental benefits of APUs, the federal government took the step to increase the maximum gross weight limit and axle weight limit by 400 pounds on vehicles that were equipped with APUs or similar qualified idle-reduction technology. However, although this was signed into law by former President Bush as part of the Energy Policy Act of 2005, it was not accompanied by a mandate. The Federal Highway Authority said after the signing that state regulations on weight limits were still pre-eminent. Although individual states began to adopt the new weight limits, the lack of a federal mandate led to confusion. The situation was confused further in 2012 after former President Obama signed a new highway bill, MAP-21, which raised the federal weight exemption to 550 pounds, again without a federal mandate for states to adopt it. Nevertheless, some states have followed through with making the 550-pound exemption into state law.

States Make Up Their Minds

The result is a situation in which some states abide by the 550-pound exemption, some still follow the 400-pound exemption, and some still have no exemption at all. For drivers with APUs it can be confusing, but the following chart should help make sense of it all. This state-by-state chart explains the current regulations regarding APU weight exemptions. However, be aware that state laws can change, so drivers and fleet professionals should always check weight allowances before traveling at or near the maximum weight capacity.

APU Exemption Guide

APU Exemption Guide created by Track Your Truck

Author bio: Robert J. Hall is President of Track Your Truck, a leader in fleet tracking systems and software for small and mid-sized companies.