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Hybrid and Other Advanced Technologies

Hybrid Technologies

Also called idle-stop or smart-start

These systems automatically turn the engine off when the vehicle comes to a stop and restart it instantaneously when the the brake is released or the accelerator is pressed. This reduces fuel wasted during idling.

Potential Efficiency Improvement: 2%1
Savings Over Vehicle Lifetime: *

Also called integrated starter generator (ISG), belted alternator starter (BAS), electronic assist (eAssist)

These systems use Stop-Start technologies to reduce idling. Regenerative braking is also used to convert mechanical energy lost in braking into electricity. The electricity is stored in a battery and used to power the automatic starter and to aid in acceleration for very short distances.

Potential Efficiency Improvement: 3%–6%1
Savings Over Vehicle Lifetime: *

Full hybrids use Stop-Start systems and regenerative braking. Compared to mild hybrids, they use a larger battery and a more powerful electric motor. This allows the electric motor to assist the engine or propel the vehicle by itself at lower speeds. They can also travel much farther using electricity than mild hybrids.

Potential Efficiency Improvement: 27%–35%1
Savings Over Vehicle Lifetime: *

Other Technologies

It takes less energy to propel a lighter vehicle than a heavier one. Manufacturers are reducing weight by designing vehicles to use less material, using lighter weight materials, and downsizing the powertrain. Weight can be reduced without reducing vehicle size, safety, or riding comfort.

Potential Efficiency Improvement: 1%–3% per 5% reduction in weight1
Savings Over Vehicle Lifetime: *

When rolling, a tire is continually deformed by the load of the vehicle on it. This causes energy loss. Manufacturer changes to tire shape, materials, and tread design can reduce rolling resistance and improve fuel economy.

Potential Efficiency Improvement: 1%–3%1
Savings Over Vehicle Lifetime: *

* Fuel cost savings are estimated assuming an average vehicle lifetime of 166,000 miles,2 a fuel price of , and an average fuel economy of 25.2 MPG.3 All estimates are rounded to the nearest hundred dollars.

View Data Sources…
  1. National Academy of Sciences. 2015. Cost, Effectiveness and Deployment of Fuel Economy Technologies for Light-Duty Vehicles. The National Academies Press, Washington, D.C. To be conservative, most values have been rounded down to the nearest percent.
  2. Average MPG for 2017 vehicles based on Light-Duty Automotive Technology,Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 Through 2017.Adobe Acrobat Icon. EPA, 2017. Table 2.1.
  3. Average of car and truck lifetime mileage estimates (rounded to the nearest thousand miles) based on Transportation Energy Data Book, Edition 36.2. Oak Ridge National Laboratory. Table 3.13.

This website is administered by Oak Ridge National Laboratory for the U.S. DOE and the U.S. EPA.