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How to Choose the Best APU Unit for Your Semi Truck

Choosing the right Auxiliary Power Unit (APU) for your semi truck is crucial for enhancing your vehicle's efficiency, comfort, and cost savings. In this guide, we will compare diesel and electric APUs, delve into the specifics of AGM and lithium battery-powered electric APUs, and highlight the best options available on the market.

What is an Electric APU?

An electric APU is a device that provides power for heating, cooling, and other electrical needs in a truck cab without requiring the main engine to run. This not only saves fuel but also reduces emissions and wear on the engine, making it a highly efficient solution for long-haul truckers.

Diesel vs. Electric APUs

1. Diesel APUs

Diesel APU

Diesel APUs use a small diesel engine to provide power for heating, cooling, and electrical needs when the main engine is off. Here are some key points:


Widely Available: Diesel APUs are common and can be serviced easily.

High Power Output: Capable of handling significant power loads for extended periods.


Fuel Consumption: Diesel APUs consume additional fuel, leading to higher operating costs.

Emissions: They produce emissions, which may not comply with all environmental regulations.

Maintenance: Requires regular maintenance similar to any other diesel engine.

High Initial Investment: Most common Diesel APUs are between $10,000 to $15,000 installed. The high initial investment is a big problem for many small fleets and owner-operators.

2. Electric APUs

Electric APUs utilize battery power to provide the necessary energy for truck systems. Polar Fox electric APUs, for example, are designed to be eco-friendly and cost-effective.


No Fuel Consumption: Runs on batteries, eliminating additional fuel costs.

Zero Emissions: Environmentally friendly with no emissions.

Lower Maintenance: Fewer moving parts mean less maintenance compared to diesel APUs.


Initial Cost: Some electric APU providers charge similar price as Diesel APU.

Battery Management: Requires efficient battery management and periodic charging.

AGM Battery vs. Lithium Battery Electric APUs

1. AGM (Absorbent Glass Mat) Batteries

AGM batteries are an older technology often used in electric APUs.


Reliable: Proven technology with stable performance.

Lower Initial Cost: Generally cheaper upfront than lithium batteries.


Weight: Significantly heavier (three times or more) than lithium batteries for the same capacity.

Charging Speed: Slower charging rates, which can be inefficient.

Maintenance: Requires an expensive alternator upgrade to handle the charging speed.

2. Lithium Batteries

Lithium batteries represent the latest in battery technology, offering several advantages over AGM batteries.


Lightweight: Much lighter than AGM batteries, reducing the overall weight of the truck.

Fast Charging: Charges much quicker, improving efficiency.

Longer Lifespan: Generally lasts longer and can handle more charge-discharge cycles.


Higher Initial Cost: More expensive upfront than AGM batteries.

Heat Sensitivity: Can be sensitive to extreme temperatures, although advanced systems mitigate this issue.

Comparison of Key Factors

1. Price

Diesel APUs: Lower initial cost but higher operating costs due to fuel and maintenance.

Electric APUs with AGM Batteries: Moderate initial cost but less efficient charging and heavier weight.

Electric APUs with Lithium Batteries: Higher initial cost but greater efficiency and longer-term savings.

2. Simplicity and Installation Time

Diesel APUs: Installation can be complex due to the integration with the truck’s fuel system.

Electric APUs with AGM Batteries: Simpler than diesel but still requires consideration of charging systems.

Electric APUs with Lithium Batteries: Simplest installation, especially with advanced systems like those from Polar Fox APU.

Why Choose Polar Fox Electric APU?

Polar Fox APU stands out as a leader in the electric APU market, providing the most advanced and affordable electric APUs for semi trucks. Here’s why:

Innovative Technology: Our APUs use cutting-edge lithium battery technology, ensuring lightweight, fast-charging, and long-lasting performance.

Cost-Effective: Thought Polar Fox APU is equipped with the most advanced starting lithium batteries, we managed to offer the most completitive price for our entry level V-Model for just $5,500 installed.

Environmental Commitment: Our APUs produce zero emissions, helping you stay compliant with environmental regulations.

Easy Installation: Designed for quick and straightforward installation, reducing downtime for your truck.

Comprehensive Warranty: We offer industry-leading warranties, giving you peace of mind with your investment.


When choosing the best APU unit for your semi-truck, consider the long-term benefits of electric APUs, especially those with lithium batteries. Polar Fox APU provides a superior solution that balances advanced technology, cost efficiency, and environmental responsibility, making it the best choice for your trucking needs.

For more information and to explore our range of electric APUs, visit Polar Fox APU.

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