How Do Hybrid Cars Work?

Hybrid cars are becoming increasingly popular by the day. But not all hybrids are the same. There are three main designs for hybrid cars, which each work in different ways.

Mia Bevacqua
3-minute read

BMW i8 Parallel Hybrid Sports Car

Nowadays, hybrid cars are more common than Starbucks. You’ll find one on almost every corner, even in places that used to be exclusively pickup truck country. Hybrids are becoming more mainstream by the day. There are dozens of hybrid cars available from almost every brand, and they all use one of three basic powertrain designs. What are the differences between the kinds of hybrids?

Series Hybrid

Series Hybrid System

Remember when Chevrolet introduced the Volt? It was supposed to be the best thing since sliced bread. Unfortunately, the fact that it could barely make it around the block on electric power alone squashed the hype. The Volt is not a pure electric vehicle. Rather, it uses a series hybrid powertrain. In this type of hybrid, the wheels are turned exclusively by an electric motor, but the electricity for that motor comes from another source, such as an internal combustion engine. The engine is connected to a generator, which in turn is used to either charge the batteries or power the electric motor. Since the gasoline engine is connected only to the generator, it never directly powers the drive wheels. Most series hybrids allow plug-in charging to minimize fossil fuel use. The main drawback of this design is that an engine must be dragged along just to keep the hybrid batteries charged. However, since that engine is usually gas-powered, it’s easy to refuel at any gas station, making longer trips easier.

Parallel Hybrid

Parallel Hybrid System

The parallel design sandwiches the transmission between an electric motor and internal combustion engine. With this design, one or both of the power sources can be used for vehicle propulsion. Under most driving conditions, the electric motor is used to assist the internal combustion engine. If you need to engage in a stop light drag race, both the gas engine and electric motor can work together to provide maximum acceleration. During deceleration, the electric motors run in reverse, acting as generators to recharge the batteries. One disadvantage of the parallel design is that oodles of complex software must be used to effectivly blend the two different power sources. This design can be found in the stunning BMW i8 sports car and 218-MPH Porsche 918 Spyder.

Series-Parallel Hybrid

Series Parallel Hybrid System

The most famous hybrid of all, the Toyota Prius, employs the series-parallel design. Like the name implies, this setup combines functions of both the series and parallel hybrid. To accomplish this, a power split device (similar to a manual transmission clutch) is used to allow the electric motor to operate on its own or with the help of the internal combustion engine. The engine is also used to charge the batteries, like in a series hybrid, which is why it may run even when the vehicle is stopped. Thanks to its efficiency, series-parallel is the most common hybrid design on the road today.

Even though many consumer still choose gargantuan SUVs, there is no doubt hybrids are here to stay—many of those SUVs are available as hybrids, too. There’s something rewarding about using technology to stick it to the man. If you’re ready to escape the tyranny of the oil industry, a hybrid might be the vehicle for you, and there are more and more options to choose from hitting the road every day.


Mia Bevacqua works at YourMechanic.com. Have your own question about service terms or anything else auto related? You can ask one of our highly trained technicians and get an answer quickly, usually within 24 hours. 

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