APU ROI calculator
By Fernandez · Updated October 2026
Work out when an auxiliary power unit pays for itself on your truck.
Net saved per year
$2,820
Payback
51 months
Five-year result
$2,100
Leaves out engine wear avoided and anti-idling fines, which can add to the savings, and any resale value of the unit.
Less idle time saves fuel; less waiting at the dock saves more. We plan loads so the truck waits less.
Our dispatchers find and negotiate the loads; you approve each one and sign the rate con. 5% of gross for one truck with an MC 6 months or older, no setup fee.
Start dispatchHow it is calculated
- Fuel saved per hour = engine idle burn - APU burn.
- Net saved per year = idle hours avoided x fuel saved per hour x diesel price - APU maintenance.
- Payback months = APU cost / (net saved per year / 12).
- Five-year result = net saved per year x 5 - APU cost.
Worked example
| Item | EXAMPLE |
|---|---|
| APU installed cost | $12,000 |
| Idle hours avoided per year | 1,500 |
| Engine idle burn and APU burn | 0.8 and 0.2 gallons an hour |
| Diesel price | $3.80 |
| APU upkeep | $600 a year |
| Net saved per year | $2,820 |
| Payback | about 51 months |
| Five-year result | $2,100 |
EXAMPLE assumptions, not a quote or a measured burn rate.
What the result means
If payback lands inside the time you plan to keep the truck, the APU likely makes sense on fuel alone, before counting engine wear and comfort. If it lands after you plan to sell, the case is weaker, unless an APU adds resale value or you run in places with strict idling rules. The single biggest input is idle hours: count your real nights in the truck for a month.
Waiting is idle time too. Fewer hours sitting at docks means less idling, which is part of why load planning matters. Compare the APU against other uses of the money, such as paying down the truck with the truck refinance savings calculator, and check load-level costs with the load profitability calculator. Equipment financing and value are covered in commercial truck financing rates and semi truck depreciation by age and mileage.
Mistakes that skew APU math
- Guessing idle hours. Pull the idle time from your ECM report or ELD for a month instead of estimating; most owners guess low or high by a wide margin.
- Using the engine's best idle burn. Burn rises with high idle and cab heating or cooling, which is exactly when an APU runs.
- Forgetting the unit's own service. Filters, belts and engine oil on a diesel APU cost money every year.
- Ignoring how long you will keep the truck. A payback of four years means little if you trade the truck in two, unless the unit adds resale value.
Less waiting, less idling
We plan loads around appointments and reloads. A dispatcher calls you back.