How Do Hybrid Cars and Trucks Work?

By using both a conventional engine and electric motor, the best hybrids achieve significantly better fuel efficiency than their non-hybrid counterparts. They also pollute less and save drivers money through fuel savings.

The most advanced hybrids have larger batteries and can recharge their batteries from an outlet, allowing them to drive extended distances on electricity before switching to gasoline or diesel. Known as "plug-in hybrids," these cars can offer much-improved environmental performance and increased fuel savings by substituting grid electricity for gasoline.

Hybrid car features

The addition of a battery-powered electric motor increases the fuel efficiency of hybrids in a number of ways.

Like the switch that turns off your refrigerator's light bulb when the door is closed, "idle-off" (also known as “stop-start”) is a feature that turns off your car's conventional engine when the vehicle is stopped, saving fuel. The battery provides energy for the air conditioner and accessories while the vehicle idles at stoplights or in traffic, and the electric motor can start the vehicle moving again. If needed, the conventional engine will reengage to provide more power for acceleration. "Regenerative braking"is another fuel-saving feature. Conventional cars rely entirely on friction brakes to slow down, dissipating the vehicle's kinetic energy as heat. Regenerative braking allows some of that energy to be captured, turned into electricity, and stored in the batteries. This stored electricity can later be used to run any electric accessories and/or power the motor to accelerate the vehicle.

Having an electric motor also allows for more efficient engine design. This "power assist" feature helps reduce demands on a hybrid’s gasoline engine, which in turn can be downsized and/or more efficiently operated. The gasoline engine may produces less power, but when combined with electric motors, the system’s total power can equal or exceed that of a conventional vehicle. Reducing power demand from the engine and supplementing it with a motor can also keep the engine operating at its most efficient conditions for more of the time.

The most efficient hybrids utilize "electric-only drive," allowing the vehicle to drive entirely on electricity and use less fuel. In hybrids that can't be plugged-in, electric-only drive is typically only utilized at low speeds and startup, enabling the gas or diesel-powered engine to operate at higher speeds, where it’s most efficient.. Most plug-in hybrids—which tend to have larger batteries and motors—can drive entirely on electricity at relatively high speeds for extended distances (typically 10 to 30 miles).

Different hybrids also use different types of "drivetrains," the mechanical components that deliver power to the driving wheels. Learn about the implications of different hybrid drivetrains.

Differences between hybrids and other EVs

Hybrids that can't be recharged from an outlet aren't generally considered to be electric vehicles, as they rely exclusively on gasoline or diesel for energy. Plug-in hybrids, described above, are considered electric vehicles, along with battery electric and hydrogen fuel cell vehicles. Learn more about how plug-in vehicles work.

Battery electric vehicles Battery electric vehicles only use an electric motor and battery, eschewing conventional engines altogether. Because they don't use gas or diesel, battery electrics are often cleaner and cheaper to fuel than hybrids and conventional vehicles. Learn more about how battery electrics work.

Hydrogen fuel cell vehicles power an electric motor and battery by converting stored hydrogen gas to electricity using a fuel cell. These vehicles are available in some locations, and particularly in California. These vehicles offer some benefits—including fast refueling times and long driving ranges—but also require hydrogen refueling stations, which at present aren't widely available. Very few passenger fuel cell vehicle models are currently available, but the technology may have applications for larger on road vehicles and non-road vehicles that may be difficult to electrify with batteries such as marine and aviation applications. Learn more about electric vehicle technology, including its potential as a nationwide oil-saving solution.