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Hybrids are more efficient than comparable conventional vehicles, especially in stop-and-go driving, due to the use of regenerative braking, electric motor drive/assist, and start/stop technologies. Still, much of the energy is lost to engine and driveline inefficiencies or used to power accessories. About 25%–40% of the energy from the fuel you put in a hybrid is used to move it down the road, depending on the type of driving.

Energy Losses and Gains for a Hybrid Vehicle for Combined City and Highway Driving

Hybrid vehicle showing energy losses and gains for comined city and highway driving. Engine losses: 65%-69%, Parasitic losses: 4%-5%, Drivetrain losses: 3%-5%, Power to Wheels: 27%-38% + 5%-9% (recovered) = 32%-47%, Idle losses: near 0, Energy recovered by regenerative braking: 5%-9%

Energy Losses and Gains for a Hybrid Vehicle for City, Highway, and Combined Driving

Graph showing energy losses and gains for a hybrid vehicle (drivetrain losses, parasitic losses, engine losses, regenerative braking, and power to wheels-braking, rolling resistance, and wind resistance) for city, highway, and combined driving.

Note: The figure is primarily showing losses, but the regenerative braking gains are shown below 0%, offsetting some of the above losses.

Fact #882 Dataset

Supporting Information

Energy Losses and Gains for a Hybrid Vehicle for City, Highway, and Combined Driving
  Types of Driving
Combined City Highway
Types of Losses Energy Losses
Engine Losses 65-69% 66-72% 63-66%
Parasitic Losses, e.g. water pump, alternator, etc. 4-6% 5-7% 2-4%
Power to Wheels, dissipated as: 27-38% 25-40% 29-36%
      Wind Resistance 11-16% 6-11% 17-23%
      Rolling Resistance 7-11% 6-11% 8-11%
      Braking 9-13% 13-20% 3-4%
Drivetrain Losses 3-5% 3-5% 3-5%
Idle Losses 0% 0% 0%
Types of Gains Energy Gains
Regenerative Braking 5-9% 8-14% 2-4%

Source: U.S. Department of Energy and U.S. Environmental Protection Agency, Fuel Economy Guide website.

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