Unnecessary idling pollutes the air, wastes fuel, and causes excess engine wear. Auxiliary Power Units (APUs) are efficient generators truckers and RVs can use to help save the amount of diesel fuel being used while the vehicle is being lived in but not driven. APUs provide a larger array of comfort features for drivers looking to reduce idling. APUs can provide heat, air conditioning, power for household electrical devices and engine heat. Most devices combine a small heater, a compressor for air conditioning and an alternator. APUs may be powered by diesel fuel directly from the tractor fuel tank, or by a bank of rechargeable batteries. Diesel driven APUs can operate for 5 hours or more on a single gallon of diesel fuel. For locomotives, APUs automatically shut down the main locomotive engine idle while maintaining all vital main engine systems at greatly reduced fuel consumption.

Strategies and Greenhouse Gas Reduction

  • Investigate the potential to partner with the Puget Sound Clean Air Agency and other groups, to create a pool of money to lease Accessory Power Units (APUs) to truckers.
  • Investigate the potential to locate a Cascades Sierra Solutions station in the Tacoma/Pierce County area to carry out the retrofits of APUs and other emission reducing devices.
  • Adopt a local anti-idling ordinance. By 2015-20, it is estimated that this strategy will cause a reduction in CO2 emission levels by 3,273 tons.
  • Encourage Tacoma Rail to continue retrofitting existing locomotives with idle reduction technologies and fuel-efficient injectors. By 2010-12, it is estimated that this strategy will cause a reduction in CO2 emission levels by 1,670 tons.

Cost to the City

The cost of purchasing APUs, locating and developing an APU facility, and the cost required to market a local anti-idling ordinance is going to be relatively high.

  • Costs for APUs can range from $3500 to $9000, but are typically in the $6000 to $7000 range. Therefore, the total cost depends on how many units are purchased.


  • Puget Sound Clean Air Agency
  • Cascade Sierra Solutions
  • Washington Trucking Association
  • Tacoma Community and Economic Development Agencies
  • City drivers and households
  • Tacoma Rail customers and ratepayers
  • City of Tacoma residents and ratepayers


  • Funding not identified for plug-in stations
  • Funding not identified for Tacoma Rail retrofits
  • Funding is not yet secured


  • Financially costly to idle from a fuel consumption and an engine wear perspective
    • An APU can save five gallons (about 19 liters) of fuel a day
    • An APU can extend the useful life of the main engine by around 100,000 miles (about 160,000 kilometers)
    • Caterpillar Inc. cautions drivers to "... Avoid excess idling. If the vehicle is parked for more than five minutes, stop the engine. Excessive idling can cause carbon buildup and/or excessive idling can cause the engine to slobber. This is harmful to the engine."
    • IC Corporation's engine manual states that "...Excessive idling reduces fuel economy, and may decrease oil life."
    • Cummins Inc. suggests idling for only three to five minutes before operating with a load.
  • Reduce air pollution
    •  Exhaust from excessive idling can be a health concern; ex: cancer, asthma 


  • Tacoma Community and Economic Development Agencies
  • Puget Sound Clean Air Agency
  • Cascade Sierra Solutions
  • Washington Trucking Association


  • Need to partner with the private sector
  • Need to partner with local economic development agencies
  • Need to acquire funding

Success Stories
Portland, Oregon
has implemented an objective to increase the use of highly fuel-efficient and alternative-fuel engines in on-road and off-road vehicles as well as in stationary applications:

  • Government Actions
    Educate all employees on fuel-efficient driving practices, such as avoiding unnecessary idling.
  • Community Initiatives
    Work with vehicle maintenance providers to educate consumers about the potential savings and impact on fuel consumption of maintaining vehicles properly and practicing fuel-efficient driving techniques.

Charlotte, North Carolina has implemented an anti-idling policy. In October 2004, the Charlotte Area Transit System (CATS) implemented an Anti-Idling Policy for all CATS vehicles. CATS-owned transit and service vehicles are not permitted to idle for more than 10 minutes at a CATS Operations Facility or while in service (including layover) and not idle for more than 5 minutes in an enclosed area, unless in an extraordinary operating condition. This has proven to be very effective in reducing the fuel consumption by CATS vehicles by as much as 20 percent.

Seattle, Washington has implemented a plan to significantly reduce emissions from diesel trucks, trains and ships:

  • Action #8 - Reducing diesel emissions from freight transportation requires several strategies:
    • Decreasing congestion along freight corridors to improve freight travel times;
    • Running freight on cleaner fuels, where feasible;
    • Reducing unnecessary idling by ships, trains and trucks; and
    • Improving truck fuel efficiency.