Hybrid vehicles

Hybrid vehicles pair a battery pack and at least one electric motor with a gasoline-powered engine. The battery pack is charged by harvesting energy from the gas engine and regenerative braking, which then powers the electric motor to help with acceleration and low-speed driving where electric motors are more energy efficient than gas engines. This leads to greater overall efficiency than comparable gas-only vehicles.

“Hybrid” most generally refers to a hybrid electric vehicle (or HEV), one which uses a gasoline engine and at least one electric motor for power, but which does not need to be plugged in to charge. They offer significant improvements in fuel efficiency over similar gas cars.

A “mild hybrid” is very much like a traditional gasoline car with a more powerful electrical system that relieves some of the engine’s load. Mild hybrids offer slight efficiency gains over traditional gas cars.

A plug-in hybrid (or PHEV) uses a larger battery and more powerful electric motors–it can be plugged in and charged up and is able to drive on electric power alone. Depending on how you drive it, a PHEV can run on very little gas.

Because they need battery packs, hybrid cars tend to weigh more and cost more than similarly-sized gasoline cars. These battery packs will also need to be replaced eventually as their capacity diminishes over time, which can be a significant added cost for high-mileage hybrids.

Although the Toyota Prius has earned a spot as the poster child for hybrids, choosing the best hybrid depends on your needs. Currently there are hybrid sedans, hatchbacks, SUVs and even trucks. Luxury and performance hybrids and plug-in hybrids are also available. Basically, any vehicle category you could be shopping in likely has a hybrid of some sort available.

The most common mild hybrids use a small electric motor that acts as a starter and generator, and can provide some extra assistance to the engine. Mostly, the stronger electrical system improves efficiency by running accessories like the air conditioning pump and water pump that are traditionally driven by belts, taking some load off the engine. They don’t rely on their electric motors for acceleration, like hybrid electric vehicles do.

Energy must be used to get any vehicle up to speed, and typically that energy comes from either a fuel source or battery pack in your car. 

With a traditional braking system, pushing your foot on the pedal triggers the brake components to compress together, creating resistance to slow your vehicle's wheels. Any energy you had used to get up to speed is then lost as heat. 

With a regenerative braking system, your wheels are connected to a motor that recaptures some of the energy used to get your vehicle up to speed, which is then converted back to stored power in the battery—hence the name 'regenerative'. 

Most electric vehicles, including full EVs, HEVs, and PHEVs, feature both braking systems and allow you to select whether to use both or only regenerative braking. Because most regenerative braking systems kick in immediately after releasing your accelerator pedal (no need to apply the brake pedal) you can drive while using your traditional brakes significantly less often; this is commonly called one-pedal driving.