Long-haul truck drivers spend countless hours on the road, often stopping to rest where they need electricity to power heating, cooling and electronic equipment.
Traditionally, truck drivers keep their engines idling to maintain these features, but this practice results in increased fuel consumption, engine wear and environmental damage.
That’s where auxiliary power units (APU) work in trucks. An APU is an independent power source that allows truck drivers to operate essential systems without keeping the main engine running in idle mode.
In this article, we will discuss in detail what an APU is, how it works, its types, benefits and other key aspects.
What is An APUs On a Semi-Truck?
An auxiliary power unit (APU) is a small, secondary engine or battery-powered system installed on a semi-truck to provide power for functions such as air conditioning, heating and electrical equipment in the truck’s cabin even when the main engine is off, allowing drivers to park their trucks and remain comfortable without wasting any extra fuel.
This APU unit helps drivers reduce fuel consumption, reduce wear and tear on the main engine and comply with anti-idling laws in many states.
How Does an APUs Work in Semi-Truck?
An APU operates separately from the truck’s main engine. Depending on its type, it can either generate power using a small diesel engine or rely on battery storage. The power generated is then used to run various systems, such as:
- Climate Control – Air conditioning and heating for a comfortable rest environment.
- Electronics & Appliances – Charging devices, powering a microwave, TV, or refrigerator.
- Battery Charging – Helps maintain truck battery levels when parked for extended periods.
Types of Semi-Truck APUs Unit
The type of APU depends on the size of your truck and your needs. Semi trucks are usually equipped with two types of APUs, which run on fuel or batteries. Let’s know the difference between these two types of APU units.
#1. Combustion APUs (Diesel, Natural Gas or Propane)
These units have small diesel or gas-powered engines that generate electricity. They operate independently of the truck’s engine and can run for long periods of time. Such APU units are robust enough to supply power for cabin heating needs
Advantages
- Longer runtime.
- Can generate more power than battery-powered units.
- Operates in extreme temperatures.
Disadvantages
- Requires fuel (although much less than idling the main engine).
- Requires regular maintenance like oil changes and filter replacement.
#2. Battery-Powered APUs
Battery-powered APUs use rechargeable batteries to store and provide energy. They are often charged by the truck’s alternator while the engine is running.
Advantages
- Zero emissions, which makes them environmentally friendly.
- Quiet operation for uninterrupted sleep.
- No additional fuel consumption.
Disadvantages
- Limited operating time (typically 8-10 hours before needing a recharge).
- Battery life degrades over time, requiring replacement.
Benefits of Using an APUs On Trucks
Truck APUs save fuel, reduce engine wear, and power your cab essentials without stopping. Let’s understand its benefits in detail.
#1. Fuel Savings
Idling a truck engine for extended periods consumes a significant amount of fuel. APU systems drastically reduce fuel consumption by eliminating unnecessary idling. Some studies estimate that an APU can save up to $5,000–$7,000 per year in fuel costs.
#2. Reduced Engine Wear and Maintenance Costs
Idling increases wear on the main engine, leading to more frequent maintenance and a shorter lifespan. By using an APU, truckers can extend engine longevity and reduce maintenance expenses.
#3. Environmental Benefits
Many states have strict anti-idling laws to curb pollution. APUs help truckers comply with these regulations by providing an alternative power source, significantly reducing emissions and environmental impact.
#4. Enhanced Driver Comfort
Long-haul truckers rely on APUs to maintain a comfortable cabin temperature and power essential appliances. This allows for better rest, improving safety and well-being on the road.
#5. Regulatory Compliance
Several U.S. states impose fines for excessive idling. APUs allow truckers to avoid these penalties while ensuring compliance with state and federal laws.
Anti-Idling Laws and APUs Exemptions
Many states, including California, New York, and Texas, have strict laws limiting truck idling to 5 minutes or less in most cases. However, some states offer exemptions for trucks equipped with APUs.
The Environmental Protection Agency (EPA) promotes APUs as an effective solution for reducing emissions and fuel waste.
Truckers should verify individual state laws, as some require CARB (California Air Resources Board)-approved APUs that meet emission standards.
How To Choose the Right APUs For Your Truck
When selecting an APU, consider the following factors:
- Power Needs – Determine how much power is required for your truck’s HVAC system, electronics, and appliances.
- Fuel Efficiency – Compare the fuel consumption of diesel-powered APUs to battery-powered options.
- Budget & Cost Savings – Consider both initial investment and long-term savings.
- Weight & Space – Some APUs are bulky and may add weight to your truck.
- Maintenance Requirements – Diesel APUs require regular maintenance, while battery APUs need battery replacements.
Top APUs Brands for Trucks
Many manufacturers produce high-quality APUs. Some of the best options include:
- Thermo King TriPack Evolution – A popular diesel-powered APU with great fuel efficiency.
- Carrier ComfortPro – Known for its durability and extensive power features.
- RigMaster Power – Offers a compact design with strong power output.
- Green APU – Offers advanced emissions controls for environmentally conscious truck drivers.
- Bergstrom NITE System – A leading battery-powered APU with quiet operation.
How to Install an APUs on a Semi Truck?
Installation Process
- Installing an APU requires professional expertise. The process includes:
- Mounting the unit on the truck’s chassis or behind the cab.
- Connecting fuel lines (for diesel APUs) or integrating it with the truck’s electrical system (for battery APUs).
- Installing climate control and electrical connections.
- Testing for proper operation.
APUs Maintenance Tips
To keep an APU running efficiently, regular maintenance is necessary:
- For Diesel APUs:- Check oil levels, replace filters, and inspect belts.
- For Battery APUs:- Monitor battery health and ensure proper charging.
- General Inspections:- Clean air vents, check for leaks, and address any system malfunctions.
Cost of an APUs
| APU Type | Initial Cost | Annual Maintenance Cost | Estimated Fuel Savings (Per Year) |
|---|---|---|---|
| Diesel APU | $8,000 – $12,000 | $500 – $1,500 | $5,000 – $7,000 |
| Battery APU | $5,000 – $8,000 | $300 – $800 | $3,000 – $5,000 |
Although the initial cost of APU installation in a truck is quite high, truck drivers recoup the investment through fuel savings, reduced maintenance, and compliance with anti-idling laws.
Other Factors To Consider
In addition to fuel savings, comfort, and regulatory compliance, truckers should evaluate the following factors when considering an APU:
#1. Durability & Reliability
- Consider how well an APU performs in extreme weather conditions.
- Check for manufacturer warranties and customer reviews for long-term reliability.
#2. Noise Levels
- Some diesel APUs can be noisy, which may disrupt sleep.
- Battery-powered APUs offer quieter operation, ideal for noise-sensitive areas.
#3. Weight & Space Constraints
- Some APUs are bulky and add extra weight to the truck, which could impact fuel efficiency.
- Compact units are preferable for smaller trucks with limited mounting space.
#4. Ease of Installation & Maintenance
- Consider whether a professional installation is required.
- Look for APUs with user-friendly maintenance features like easy access to filters and batteries.
#5. Resale Value & Long-Term Investment
- APU-equipped trucks tend to have higher resale value.
- Investing in a quality APU can offer significant long-term savings.
Conclusion
An APU is an essential investment for long-haul truckers, providing significant benefits in fuel savings, environmental impact, and driver comfort. Whether opting for a diesel-powered or battery-powered unit, truckers can enhance efficiency and reduce operational costs.
With increasing regulatory restrictions on idling, installing an APU is not just a convenience but a necessity for modern trucking operations.
Before purchasing an APU, truckers should assess their specific needs, compare models, and ensure compliance with state regulations. Investing in a high-quality APU leads to long-term savings and a more comfortable, eco-friendly trucking experience.
FAQs for Truck APUs (Auxiliary Power Units)
Why should I use an APU in my truck?
Using an APU reduces fuel consumption, reduces engine wear, and helps you comply with anti-idling laws while keeping your cab comfortable.
How often should I have my APU serviced?
Depending on the model, routine maintenance, including oil changes, filter replacements, and inspections, should be performed after every 500-1,000 hours of operation.
What are common problems with APUs?
Common problems include battery failure, fuel line problems, overheating, and electrical failures. Most of these problems can be prevented with regular maintenance.
Can I install an APU myself?
Some battery-powered APUs are easy to install if you have experience, but diesel APUs usually require professional installation to ensure proper integration with the truck’s electrical and fuel systems.
Banty Paul, owner and founder of Auto Repair Zone, brings over 14 years of hands-on experience in automotive repair and maintenance. This blog was created to share expert troubleshooting guides, repair tips, maintenance advice, and cost estimates for cars and semi-trucks.
