What does a failed APU cost day to day?
Idling a big diesel overnight burns fuel and adds engine hours, and some states and cities restrict idling. Over a few weeks, the extra fuel and wear can rival the cost of the repair.
Diesel APUs have their own small engine that needs oil changes and filters; electric units rely on batteries that wear out. Many failures trace back to skipped maintenance, so ask the shop what failed and why.
Repair, replace, or switch to electric?
If the diesel APU engine is worn, replacement may beat repair. Some carriers switch to battery-electric units to cut maintenance, though they depend on charging and battery health. The right choice depends on routes and climate.
Get quotes for both repair and replacement, and estimate the fuel you burn idling per night. That number helps you see how quickly a working APU pays for itself.
How do I estimate the fuel an APU saves?
Multiply the nights you sleep in the truck by the hours you would otherwise idle and by your engine’s idle fuel burn. Compare that with the APU’s own fuel or charging use.
Your engine maker or ELD may report idle fuel use; many telematics systems show it per truck. Add the cost of extra engine hours, which bring forward oil changes and overhauls. With those numbers, the repair or replacement decision becomes a simple payback calculation instead of a guess.
| Choice | Upfront cost | Trade-off |
|---|---|---|
| Repair existing diesel APU | Lower | Unit may keep aging |
| New diesel APU | Higher | Strong heating and cooling, needs maintenance |
| Battery-electric APU | Higher | Quiet, fewer engine parts, depends on batteries |
Worked example: replacing a worn diesel APU
A two-truck fleet averaging $37,000 in monthly deposits replaces a worn diesel APU for $9,800 after weeks of idling overnight. Using an illustrative factor rate of 1.25, $9,800 would mean $12,250 repaid over roughly 6 months: 26 weekly payments of about $471.
That works out to about $2,042 a month, or 5.5% of the $37,000 this business deposits monthly, and the total cost of the money is $2,450. Cutting overnight idling saves fuel every week, which helps cover the payments while the truck keeps running long hauls.
For comparison, repaying the same $12,250 over 4 months would lift the monthly outlay to about $3,062, or 8.3% of deposits, so ask for both terms in writing; the shorter one frequently prices lower even though each payment is larger.
| Average monthly deposits | $37,000 |
|---|---|
| Amount funded | $9,800 |
| Factor rate (illustrative) | 1.25 |
| Total repaid | $12,250 |
| Cost of the funding | $2,450 |
| Term | about 6 months |
| Weekly payment (26 payments) | $471 |
| Payments as a share of deposits | 5.5% |
Who APU funding fits
Usually a fit
- Long-haul drivers who sleep in the truck most nights
- Carriers running through areas with idling limits
- Fleets trying to cut fuel spend
When to skip it
- Local drivers who rarely sleep in the cab
- Minor APU repairs you can pay from a normal week
- Businesses without recent deposits
What you’ll typically need
- Recent business bank statements
- APU quote
- Truck VIN
- Business details
Frequently asked questions
Is an APU worth repairing on an older truck?
Often yes if you run long haul, because idling costs add up quickly. Compare the repair cost with fuel saved.
Can funding cover an electric APU?
Yes. Working capital can be used for any APU type or installation.
How long does approval take for an APU?
Requests to fund an APU usually get a decision the same day when the file is complete, and funding commonly follows in a business day or two.
Does a 500 credit score rule me out for an APU?
No. Applicants from 500 can be reviewed for an APU; the deposit history does most of the work, and better credit typically improves the terms you are offered.
Idling every night because the APU died?
Apply in minutes; one application, no obligation.
Updated October 6, 2026