How Much Fuel Does a Semi Truck Consume?

A typical long-haul drive can log 1,800 hours of idle time in one year. In this article, we review average semi-truck idle fuel consumption, ideal idling rpm, and truck idling laws by state.

Idling occurs when the driver leaves the truck running in a parked position. A driver might idle their vehicle if they are making a quick visit to a truck stop or stuck in traffic. They will also idle their truck in cold conditions at night when running their personal appliances, such as a TV or a microwave.

Semi Truck Idle Fuel Consumption

A semi-truck can burn 0.6 to 1.5 gallons of fuel per hour when idling, averaging around 0.8 gallons per hour. Idling can be expensive to drivers, costing them around $40-$60 a night, depending on the fuel price. The fuel used during idling takes away from the fuel needed to drive on the road. Trucking companies also lose money from idling as truck drivers must fuel up more often to replace the fuel burned from idling.

Truckers work around the cost of idle fuel consumption by using Auxiliary Power Units(APU) to supply power to their appliances without requiring them to idle the truck. An APU can provide enough power to run the air conditioning, heater, and TV without wasting as much fuel. APUs cost around $8,500 to $13,000 to purchase and install. While the upfront cost is expensive, the APUs can save the truckers money and have a Return on Investment(ROI) of about 2.5 years.

Courtesy of Freightcourse

Besides costing truckers thousands of dollars a year, semi-truck idling also destroys the reputation of truck companies and the health of their drivers. The exhaust pouring into the air from a semi-truck will naturally be associated with the company on the name of that truck. These emissions are full of toxins and carcinogens that have been shown to lead to respiratory problems, cancer, and other diseases. Keeping the environment and drivers healthy not only is the right thing to do, but it also improves the image of a trucking company.

Ideal Idling RPM

While idling is not a recommended practice, it can be necessary to maintain comfortable temperatures during extreme weather conditions. To safely idle a semi-truck, it is essential to keep the Rotations Per Minute(RPM) between 900 to 1200 to ensure the engine has enough oil.

To reach this threshold while idling:

  • While the truck is on, shift into neutral
  • Turn the cruise control on
  • Click accelerator button
  • Raise RPM until you get within the range


When the RPM is too high, it causes engine wear and wastes fuel. Idling with too low of an RPM also causes frictional wear as oil does not spread properly. Raising the RPM also raises the oil pressure, which is necessary to keep the engine running smoothly.

Besides keeping the RPM in range while idling, it is also important to:

  • Crack the window for fresh air to avoid inhaling exhaust fumes
  • Check for any exhaust leaks
  • Never leave the truck unattended
  • Park the truck relative to wind flow to blow away any fumes underneath the truck

Truck Idling Laws by State

Not only is idling bad for the engine, but semi-truck idle fuel consumption is also bad for the environment. Idling a truck releases harmful chemicals and greenhouse gasses into the atmosphere that have been shown to contribute to climate change. To combat this, many states have created truck idling laws to reduce the amount of air pollution caused by trucks. These laws define how long a trucker can idle their truck and in what instances idling is allowed.

Here’s a list of States that have idling laws for truckers:

  • No idling: Wyoming
  • 3 minutes: Delaware, DC, Hawaii, New Jersey, Virginia
  • 5 minutes: California, Maine, Maryland, Massachusetts, New Hampshire, New York, Oregon, Pennsylvania, Rhode Island, Texas, Utah
  • 10 minutes: Illinois, South Carolina
  • 15 minutes: Nevada, West Virginia

Truck idling laws are also circumstantial and can vary depending on where you are and the nature of your idling. Laws can also change on a local level as cities can have their own set of laws pertaining to truck idling.

Semi-truck idle fuel consumption hurts both the driver and the people around them. If idling is absolutely necessary, do it for the shortest time possible, as it wastes gas, hurts the environment, and could potentially cause you legal problems.