Auxiliary power units (APUs) are one of the best weapons truck drivers can have against wasting fuel. They make 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. APUs significantly reduced emissions and fuel consumption but were not practical in many cases because of their tendency to affect weight limits.
