Truck APU: Fuel Use & Comparison

Updated November 9, 2026

A truck APU, or auxiliary power unit, supports sleeper comfort and electrical needs while the main engine is off. Choosing an APU for a semi truck involves more than a fuel-use figure: your rest hours, climate, appliances, mounting space and access to maintenance all matter.

What is an APU in a truck?

A diesel APU uses a smaller engine to produce energy. A battery APU draws on stored electrical energy. Depending on the system and installed accessories, these solutions can support air conditioning, heating, battery charging and compatible appliances. A sleeper air conditioner alone does not necessarily provide all of those functions.

What does the offered Go Green APU™ configuration do?

Nominal cooling and heating capacity of 26,000 BTU/h; cab conditions and installation affect the result.
A 4.0 kW generator for compatible loads. Running and starting demand must be checked before using several appliances together.
A manufacturer-listed 12 V, 60 A alternator for truck battery charging, with connections matched to the truck.
Power for a compatible main-engine block heater. Confirm the heater, wiring and accessories included in your quote.

We offer new and remanufactured units. Ask about the specific model and written configuration. Charging does not restore damaged batteries, and a rated generator capacity does not mean every appliance can run at the same time.

APU fuel consumption: calculate your own example

Go Green APU™ lists 0.23 US gallons per hour as a consumption reference, approximately 0.87 liters. Actual use varies with load and conditions. Measure your main engine’s idling use rather than assuming every truck consumes the same amount.

Illustration, not a measured result: assume the main engine uses 1.00 US gal/h at idle and the APU uses 0.23 US gal/h for 8 hours on 250 days per year. The fuel difference is (1.00 − 0.23) × 8 × 250 = 1,540 US gallons per year. Change the inputs to match your route.

Multiply that difference by the fuel price you actually pay to estimate the fuel-only benefit. Then include APU maintenance, financing and installed equipment costs before estimating net savings or payback. This example does not guarantee a saving, return period or maintenance-cost reduction.

Diesel vs. electric APU for a semi truck

What to compare	Diesel APU	Battery APU
Energy and duration	Uses fuel while generating energy; plan fuel and service.	Depends on stored energy, loads and the opportunity to recharge.
Heating and cooling	Review the installed HVAC system and controls.	Check cooling runtime and how heat is supplied; some configurations use a separate fuel heater.
Ownership	Engine oil, filters and other component checks follow the unit’s manual.	Battery condition, charging equipment and other component service affect operation.

An electric APU search can also lead to 12 V or 24 V air-conditioning equipment. Compare the complete system you need. This comparison does not mean The Truck Savers™ offers every technology or brand described.

Which is the best APU for your truck?

Compare actual configurations: climate capacity, electrical loads and starting demand, hours between charging or fueling, installed weight, mounting and service clearance, warranty and service access. A single BTU or watt figure does not establish the best choice for every driver.

APU maintenance and battery charging

The Go Green APU™ specification lists a 1,000-hour oil-change interval. Follow the manual for the specific model and serial number; inspections of belts, filters, fluids and cooling airflow may have other intervals or require earlier attention. Keep an operating-hours and service log.

For service or repair support, provide the model, serial number, operating hours, symptoms and location. Confirm the work, parts and appointment before changing your route. Warranty work and other APU brands require their own review.

Choose an installation location and review financing

Share the truck make, model, year, mounting-space photos and appliances with our team. We review the installation plan and expected downtime before scheduling. Several financing options are reviewed per customer; approval, terms and payments depend on the individual application.

Contact The Truck Savers™ with your phone number, truck and location so we can review the available options with you.

Need help with your truck?

Our team of experts is ready to help you. Schedule a free "La Bailada™" inspection and discover the real condition of your truck.

Truck APU: operation, fuel use and diesel vs. battery