At the heart of every hybrid is the tandem of an
internal-combustion engine (powered by gasoline) and an electric
motor (powered by batteries). In conventional vehicles, automakers
size gas engines to provide enough power for peak acceleration, but
that level of power isn’t needed most of the time. The addition of
an electric motor allows for a smaller gas engine that uses less
In most hybrids, when the vehicle idles, the gas engine shuts off
and the electric motor is the sole source of power. The electric
motor also powers the hybrid at low speeds and supplements the gas
engine with extra oomph when the driver accelerates
quickly.
To recharge their batteries, hybrids capture kinetic energy as the
vehicle slows down, a process called regenerative braking. In
conventional vehicles, this energy is lost as heat when brakes
apply friction. But in hybrids, the electric motor helps slow the
car and transfers some of the kinetic energy to the batteries,
which store the power for future use. Hybrids’ conventional brakes
kick in when needed, such as with sudden stops. Because hybrids
recharge themselves, there’s no need to plug them into an
electrical outlet overnight.
