KNOW YOUR COSTS
Truck Idling Cost Calculator
Idling feels free at 2 a.m. — it isn't. Enter how much you idle and at what diesel price to see the cost per day and per year, the gallons you're burning, and whether an APU pays for itself.
A truck idling its main engine burns about 0.8 gallons an hour — about $5.08/hour or $10,163/year at 2,000 idle hours and $6.352/gal diesel (week of Oct. 26, 2026); a diesel APU (~0.25 gal/hr) cuts that roughly 69%; at 1,000 idle hours a year, $8,500–$13,000 installed cost pays back in about 2.4–3.7 years on fuel savings alone.
Source: DOE/Argonne National Laboratory idle-burn data; U.S. EIA diesel price ($6.352/gal, week of Oct. 26, 2026; published Oct. 27). Updated October 30, 2026.
Fuel only — this doesn't count the extra maintenance and engine-hour wear idling adds (often another $1,000–$3,000/yr), or idling-law fines. Adding paid miles shows what idling adds to your cost per mile.
What idling really costs in 2026
The main engine burns roughly 0.8 gallons an hour at idle — DOE/Argonne and fleet data put it between 0.6 and 1.0 gal/hr depending on A/C, heat, and accessory load. At the EIA national average of $6.352/gal (week of Oct. 26, 2026), every idle hour is about $5.08 in fuel. Idle 8 hours a night, five nights a week, and you'll burn around 1,600 gallons — roughly $10,163 a year in fuel alone. Maintenance and engine wear add to that fuel-only total; their cost depends on your truck and idle hours.
Idle cost per year by hours & diesel price
Annual fuel cost of idling the main engine at 0.8 gal/hr, 5 nights/week, 50 weeks/year — by idle hours per night and diesel price:
| Idle hrs/night | $4.50/gal | $6.352/gal | $6.50/gal |
|---|---|---|---|
| 4 hrs | $3,600 | $5,082 | $5,200 |
| 6 hrs | $5,400 | $7,622 | $7,800 |
| 8 hrs | $7,200 | $10,163 | $10,400 |
| 10 hrs | $9,000 | $12,704 | $13,000 |
A diesel APU (~0.25 gal/hr) cuts the fuel side ~69%; a bunk heater cuts overnight heat idling for far less. Both are usually exempt from idling laws.
Idle-reduction options compared (2026)
Idling the main engine is the most expensive way to keep the cab livable. Here's how the common alternatives stack up on fuel — per 10-hour night at $6.352/gal diesel, and per year at 1,000 idle hours:
| Option | Fuel use | Cost / 10-hr night | Fuel cost / yr (1,000 hrs) |
|---|---|---|---|
| Idle main engine | ~0.8 gal/hr | ~$51 | ~$5,082 |
| Diesel APU | ~0.25 gal/hr | ~$16 | ~$1,588 |
| Battery-electric APU | 0 gal (charges while driving) | ~$0 fuel | ~$0 fuel* |
| Bunk heater (heat only) | ~0.05 gal/hr | ~$3 | ~$318 |
| Truck-stop shore power | plug-in, ~$1–2/hr | ~$10–20 | varies by stop |
*Battery-electric APUs burn no fuel but add battery replacement (~every 3–4 years) and a higher install price, and are capped by battery capacity on long, hot nights. Diesel APU: 0.25 gal/hr × 10 hrs × $6.352 ≈ $16/night. Planning estimates — your climate, HVAC load, and equipment move them.
How the math works
- Annual idle hours = idle hrs/day × days/week × weeks/year.
- Gallons = idle hours × your burn rate (default 0.8 gal/hr).
- Idle cost = gallons × diesel price. Divide by your paid miles for the hit to cost per mile.
- APU: replaces main-engine burn with ~0.25 gal/hr; annual savings = main-engine cost − APU fuel cost; payback = installed cost ÷ annual savings.
Frequently asked questions
How much does idling cost per hour?
About $5.08/hr at 0.8 gal/hr and the $6.352 EIA diesel average. A full 10-hour break idling is about $51 in fuel — every night.
How much does idling cost per year?
Idling ~8 hrs a day, 5 nights a week burns roughly 1,600 gallons a year — about $10,163 at the EIA national average for the week of Oct. 26, 2026. That example assumes 50 working weeks. Maintenance and engine wear are additional costs.
Is an APU worth it?
At 1,000 idle hours a year, replacing 0.8 gal/hr main-engine idling with a 0.25 gal/hr APU saves about $3,494 in fuel at $6.352/gal. An $8,500–$13,000 installed cost takes about 2.4–3.7 years to recover before maintenance. More idle hours shorten payback; run your own numbers above.
Are there fines for idling?
Many states and cities cap idling (often 3–5 minutes when parked) with fines from the low hundreds into the thousands. APUs and bunk heaters are generally exempt.
What's the cheapest way to stay comfortable without idling?
For heat only, a diesel bunk heater burns ~0.05 gal/hr — about $3 a night — and is the cheapest fix. For heat and A/C, a diesel APU (~0.25 gal/hr) or a battery-electric APU pays back fastest if you idle heavily; truck-stop shore power works where it's offered. Idling the main engine is almost always the most expensive option per night.
Methodology & sources
Idle fuel burn (~0.8 gal/hr main engine, ~0.25 gal/hr APU) from DOE/Argonne National Laboratory and NACFE idle-reduction research; 2026 diesel price from the U.S. EIA ($6.352/gal, week of Oct. 26, 2026; published Oct. 27). Annual examples use 50 working weeks; maintenance and engine wear are excluded. Sources: Argonne idle-reduction research, NACFE diesel APUs, U.S. EIA. Fuel-only estimate for planning. Last updated October 30, 2026. Built by TruckMargin.
Related calculators
Idle fuel is one line in your operating cost. See your full cost per mile, compare fuel-card savings and cost per mile by truck type, then check what's actually left after the load with the owner-operator take-home pay and factoring cost calculators.