Plug-in hybrid electric vehicles (PHEV) use batteries to power an electric motor and another fuel, such as gasoline, to power an internal combustion engine (ICE). PHEV batteries can be charged using a wall outlet or charging equipment, by the ICE, or through regenerative braking.

Hybrid electric vehicles (HEV) are powered by an internal combustion engine in combination with one or more electric motors that use energy stored in batteries. An HEV cannot plug in to off-board sources of electricity to charge the battery.

Mild hybrids (MHEV) use a battery and electric motor to help power the vehicle and can allow the engine to shut off when the vehicle stops (such as at traffic lights or in stop-and-go traffic), further improving fuel economy. Mild hybrid systems cannot power the vehicle using electricity alone.

Hydrogen fuel cell electric vehicles (FCEV) use a propulsion system similar to that of electric vehicles, where energy stored as hydrogen is converted to electricity by the fuel cell. They only emit water vapor and warm air.