A hybrid vehicle has a powertrain made up of both an electric motor and an internal combustion engine. It uses this combination of power sources to improve fuel economy and reduce tailpipe emissions. A hybrid vehicle’s lower fuel consumption comes from leveraging electric power, provided by an on-board battery pack, to turn the electric motor and partially or fully motivate the vehicle, usually at lower speeds. By reducing the gasoline engine’s role in driving the hybrid’s fuel efficiency can be substantially improved over a conventional car.

Types of Hybrid Cars

While the above description covers the basic design of a hybrid vehicle, there are variations on hybrid vehicle design.

Mild Hybrid

Some early hybrid models, including the 1999 Honda Insight and 2005 Chevrolet Silverado pickup, used a mild hybrid design. These hybrids incorporate an electric motor and hybrid battery pack into the drivetrain, but both the motor and battery are relatively small, providing a bit of extra power to the engine during low-speed acceleration, then recharging the battery when the vehicle is decelerating or through regenerative braking. Beyond the relatively small motor and battery pack, a mild hybrid is defined by never moving via pure electric power – the gas engine always plays the primary role in turning the wheels.

Full Hybrid

As the name implies, a full hybrid uses electrical energy more aggressively than a mild hybrid, and can even offer pure electric driving at low speeds or for short distances. This hybrid system’s larger battery and motor use high voltage – relative to a mild hybrid – to drastically reduce the engine’s workload, thus delivering substantially better fuel economy than a similarly-sized traditional vehicle. The most famous full hybrid is the Toyota Prius, but several automakers, including BMW, Ford, Hyundai, Kia, Lexus, and Porsche, have produced and sold full hybrid sedans and SUVs.

Parallel Hybrid

Both mild and full hybrids use a parallel hybrid design. The name comes from how the electric motor is integral (or “parallel) to the gasoline drivetrain. Both the engine and electric motor are aligned, allowing either or both to power the vehicle’s wheels, either independently or working together. The battery pack, usually made of lithium ion cells, is recharged by the engine or through regenerative braking.

Series Hybrid

A series hybrid takes a different approach to saving fuel by using only its electric motor to power the vehicle's wheels while either a battery pack or on-board generator power the motor. The gasoline engine only comes on when the battery pack falls below a certain voltage, at which point the engine turns on to power an on-board generator, which sends electricity to the electric motor. In this system the engine never directly drives the wheels. The Chevrolet Volt is probably the best-known series hybrid.

Plug-In Hybrid

Because series hybrids require larger battery packs, most of them are plug-in hybrid electric vehicles, or PHEVs. But parallel hybrids like the Prius and RAV4 are also available as plug-in hybrid models. In both cases, plug-in hybrids use energy from the electric grid to charge the battery pack when the vehicle is parked. Plug-in hybrid cars use even larger battery packs than a full hybrid, and all PHEVs offer at least a limited pure electric range – usually between 20 and 50 miles. The fuel savings for PHEVs versus traditional cars is the highest due to their substantial battery power and extended pure electric range.

What is the Best Hybrid Design?

Hybrid technology has evolved and improved over the past two decades, but the real shift in recent years is the move toward more plug-in hybrid models. These make an excellent alternative to pure electric cars because their all-electric range can handle most consumers’ daily commuting needs, meaning zero fuel consumption and tailpipe emissions most of the time.

And if a driver needs to travel beyond a PHEV’s electric range, the engine is always there, ready-and-willing to fire up to keep the vehicle moving after the battery pack is depleted. Of course, like a Tesla or any other electric car, PHEVs need daily access to the electric grid to recharge, whether that comes from a level 2 charger in the owner’s garage or a public charging station.

Plug-in hybrids also appear to be future proof, as California included them, along with electric and hydrogen cars, as one of the vehicle types to be legally sold in the state starting in 2035. That’s the year California plans to ban all new car sales of traditional gasoline vehicles.

If you like the idea of rarely using gasoline, but want to avoid the range anxiety many consumers feel with an electric car, plug-in hybrids offer an excellent blend of traditional and modern automotive technology.

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