Auxiliary Power Units: APU for Trucks & Commercial Vehicles

An auxiliary power unit (APU) is a product that provides cooling, heating, and electrical power for hotel loads in the truck cab when the tractor main engine is off. It also maintains the tractor battery charge level and can be integrated into the tractor engine coolant system to improve starting capability in low ambient environments.

APUs are commonly installed on semi-trucks to increase driver comfort while reducing engine idle time and fuel consumption. APUs can be used on other large vehicles where secondary power is needed, including service cranes, bucket trucks, commercial vans, construction equipment, and aircraft.

On a truck, an APU operates independently from the main engine to supply electricity and climate control to the cab. This allows drivers to run amenities such as heating, air conditioning, electronics, and microwaves without idling the truck's main engine.

The truck APU is typically installed on the exterior frame rails, behind the passenger side fuel tank.

Yes, Thermo King APU models have the capability to charge the truck’s batteries while supplying auxiliary power.

APUs reduce the need to idle the truck's engine, which saves fuel, lowers maintenance costs, and reduces emissions.

Our TriPac APU consumes approximately 75% less fuel per hour than idling the tractor engine. That’s about 2,500 gallons per year in fuel savings, or 10,000 gallons over the typical length of tractor ownership.

An APU saves your engine for the road, not the truck stop. Eliminating unnecessary engine idling can reduce engine wear and maintenance frequency.

Additionally, an APU helps truck owners retain more of their fleet resale value by offloading valuable engine hours.

We do not recommend running the truck and the APU at the same time. The APU is designed to operate when the main engine is off. Running both may lead to unnecessary wear and technical issues.