How much fuel does a truck use idling?

About 0.8 gallons an hour for a heavy-duty truck, according to the US Department of Energy. A long-haul truck idling about 1,800 hours a year for rest uses roughly 1,500 gallons.

How long can a truck idle?

It depends where: 5 minutes in California and New York, 3 in New Jersey. In Great Britain a stationary vehicle's engine must be switched off to prevent noise or exhaust emissions. Most rules list exceptions.

What is an APU on a truck?

An auxiliary power unit: a small on-board unit that powers the cab's climate control and electrical devices while the main engine is off, so the driver can rest without idling it.

Term

Idle reduction

Idle reduction means cutting the time a truck's engine runs while the vehicle is parked, usually to give the driver heat, cooling or power during rest. A heavy-duty truck burns about 0.8 gallons of fuel an hour idling, and a long-haul truck idles about 1,800 hours a year, US Department of Energy figures show.

Also called truck idling, anti-idling, idling limits, auxiliary power unit, APU, truck stop electrificationUpdated 13 October 2026

The alternatives

Option	How it works	Consideration
Auxiliary power unit (APU)	On-board power for climate control and electrical devices, engine off	High initial cost and heavy; most states give APUs a weight exemption
Electrified parking spaces	Also called truck stop electrification or shore power: plug in, engine off	No emissions at the point of use, but limited availability
Fuel-fired heaters, heat recovery	Cab, bunk or coolant heaters draw a little fuel; heat recovery circulates engine heat after shut-off	Little or no fuel, quiet, fast payback where heat is needed
Automatic engine stop-start	Stops and restarts the engine as needed	Inexpensive, but minimal savings in extreme weather

US Department of Energy and Argonne National Laboratory, August 2015

Worked example: a year of idling

1,800 hours idling → about 1,500 gallons of diesel · × 10.18 kg CO2 per gallon = about 15.3 t CO2 · an alternative using 95% less fuel → about 75 gallons · every $1 a gallon of diesel = $1,500 a year

Hours and gallons from the DOE/Argonne idling sheet (2015), which says some alternatives use up to 95% less fuel; CO2 per gallon of diesel from US EPA. The price line is arithmetic, not a forecast.

Argonne estimates that rest-period truck idling in the US consumes up to 1 billion gallons of fuel a year, at a cost of around $3 billion. The EPA's Diesel Emissions Reduction Act program provides financial support for some idle reduction projects.

Idling limits

Where	Rule
California	Trucks over 10,000 lb gross vehicle weight rating: no idling more than 5 consecutive minutes at any location (13 CCR 2485)
New York	Heavy-duty vehicles: no idling more than five consecutive minutes when not in motion (6 NYCRR 217-3.2)
New Jersey	Three consecutive minutes (N.J.A.C. 7:27-14.3)
Great Britain	A stationary vehicle's engine must be stopped to prevent noise or exhaust emissions (Road Vehicles Regulations 1986, reg. 98)
Wales	From 30 September 2026, a fixed penalty for stationary idling of £75 to £150
Germany	Running a vehicle's engine unnecessarily is prohibited (StVO §30)

The mistake people make

Assuming automatic stop-start settles compliance. DOE notes these systems may not ensure compliance with state idling restrictions — in California a truck may idle only with a Clean Idle sticker — and intermittent engine noise may disturb a resting driver. Check each state or country the route passes through, and its exceptions.

FAQ

Idle reduction: common questions

How much fuel does a truck use idling?: About 0.8 gallons an hour for a heavy-duty truck, according to the US Department of Energy. A long-haul truck idling about 1,800 hours a year for rest uses roughly 1,500 gallons.
How long can a truck idle?: It depends where: 5 minutes in California and New York, 3 in New Jersey. In Great Britain a stationary vehicle's engine must be switched off to prevent noise or exhaust emissions. Most rules list exceptions.
What is an APU on a truck?: An auxiliary power unit: a small on-board unit that powers the cab's climate control and electrical devices while the main engine is off, so the driver can rest without idling it.