Hybrid Cars

Definitive Guide to Hybrid Cars

Definitive Guide to Hybrid Cars

What is a Hybrid Car?

Hybrid cars came on the scene in 1997 with the release of the Toyota Prius. Touting its increased fuel economy and reduced emissions, the Prius quickly became popular among many environmentalists and eco-minded celebrities.

Hybrids have continued to grow ever since, and automakers such as Toyota, Kia, Honda, Ford, Hyundai and others have built hybrid variations of their most popular models.

So, what exactly is a hybrid car? How does it work? And most importantly, should you consider one? The answer depends primarily on your driving habits and access to a charging outlet.

There are two types of hybrids that both utilize a combination of electric power and gasoline. One is a conventional hybrid vehicle often referred to as a Hybrid Electric Vehicle (HEV) and the other as a Plug-in-Hybrid Electric Vehicle (PHEV). The difference between an HEV and PHEV is that a PHEV can be plugged in to recharge whereas an HEV uses regenerative braking to recharge. Both types of hybrids can reduce fuel consumption and CO2 emissions by up to 35%.  

Here, we will explore the technology behind HEVs, highlight the advantages and disadvantages over a conventional gasoline car, and help you determine if a hybrid is the right kind of vehicle for you. Let’s pop the hood and jump in!

Electric Vehicles (EV) Cheat Sheet  
Type of CarBEVHybrids 
  HEVPHEV
NameBattery Electric VehicleHybrid Electric VehiclePlug-in Hybrid Electric Vehicle
Fuel TypeBattery OnlyGas + BatteryGas + Battery
Fuel SourceChargerGas + Regenerative BrakingCharger + Gas + Regenerative Braking

Technology

If you open the hood of an HEV, you’ll see that it looks much like a conventional gasoline car, because in many ways it is. You will see an engine, a transmission, a timing belt, etc. However, you’ll notice the engine is often slightly smaller because the hybrid battery provides extra, supplementary power. This reduces the need for a large gas engine because it simply doesn’t have to work as hard. To better understand how a hybrid car works, let’s talk about at the various components that make HEVs stand out from the rest.

Battery

There are two batteries in all HEVs: the auxiliary battery and the traction battery pack. The auxiliary battery serves the same purpose as it does in a conventional gasoline car— to supply the power to the ignition system and other accessory systems (like the radio, power windows, etc.) even while the motor isn’t running. The traction battery pack is what provides increased fuel economy and acceleration, including the full power required for low-speed acceleration.

The traction battery pack is typically made using nickel-metal hydride (NiMH) or lithium-ion batteries stacked together and located near the rear axle so that, in the case of a collision, the battery is well-protected in a fireproof metal box.

You might be wondering whether the battery is flammable or explosive. The current generation of NiMH batteries used in hybrid cars are non-explosive. Lithium-ion batteries can hold a greater charge within the same amount of physical space – but this extra charge capacity comes with a potential downside. In theory, Lithium ion batteries can be explosive under certain conditions; however, automakers and independent testing have indicated that the batteries are not dangerous because the fireproof box keeps passengers safe.

Nothing lasts forever, and batteries are no different. The lifespan of a battery can vary based on miles driven and the vehicle specs. Almost all batteries are subject to degradation with time and each vehicle has a slightly different configuration that causes the range to vary.

To learn more about batteries, read our Definitive Guide to Electric Car Range & Batteries.

Battery Warranty

Conventional gasoline cars have a mechanical warranty to cover major problems relating to the engine, transmission and other essential systems. Hybrid warranties are similar but on top of the mechanical protections, hybrid batteries often have their own separate warranty.

As an example, a 2020 Toyota Prius has a 10-year, 150,000-mile warranty on its battery. This warranty however is different from the mechanical warranty, which at the time of this article is an eight-year, 100,000-mile warranty.

Keep in mind that each automaker has its own set of terms and conditions for the warranty on their vehicles, so we suggest taking the time to fully understand which make and model is the right fit for you, your transportation needs and how long you intend to keep your vehicle.

Questions that often come up related to used hybrids are: what if I consider a used hybrid that no longer has the battery under warranty? If a replacement is required, what will it cost?

The battery cost will vary based on the year and model of the car. As an example, if we look at the 2010 Toyota Prius, the cost ranges from $3,000 to $5,000. While this is expensive, it’s worth mentioning that replacing batteries is the exception rather than the norm. For instance, a Prius can often go up to 300,000 miles without needing a battery replacement. The cost of batteries continues to decline as technology continues to improve.

Charging

One of the benefits of driving a PHEV over a traditional hybrid is that the battery can be charged by plugging it in.

You can further reduce your costs if you take advantage of off-peak electricity rates that may be offered by your local electric utility. Generally, charging your car during peak power consumption times (when everyone else in your area is awake and using electricity) can be much more expensive than if you were to do the same charge cycle overnight. Knowing when to charge is an important part of reducing the cost of ownership.

For more on electric car charging, read our Definitive Guide to Electric Car Charging.

Regenerative Braking

Since an HEV can’t be plugged in, the battery must rely on a process called regenerative braking to recharge. To fully understand regenerative braking, we have to step back and understand an energy principle of physics called kinetic energy. Kinetic energy is the energy of motion – and cars in motion have a lot of kinetic energy.

When you hit the brakes in a traditional vehicle, the energy is transferred from the body of the moving vehicle to the braking system, causing that kinetic energy (from the car’s motion) to turn into friction and heat energy as the vehicle is slowed. After a long drive you might notice your brakes will be hot. While effective at stopping the vehicle, that friction leads to wear and tear over time, which is why brake pads and/or rotors on any car will require eventual replacement.

The braking system on a hybrid vehicle is different from a conventional braking system. As soon as the driver lifts off the accelerator, even before the brake pedal is pushed, the system will start to harvest the energy from the car’s moving body, slowing it down. It does this by taking the mechanical energy and converting it into electrical energy. That energy is then sent to the battery to be stored where it will be used to power the vehicle later.

So, remember that friction and heat produced in a traditional car? In a hybrid, instead of being released and wasted as heat, the car holds onto the energy and uses it to recharge its battery.

Hybrids still have the same brake pads found in conventional cars, but they are secondary to the regenerative system. This is why brake pads on hybrids can last for up to 100,000 miles as regenerative braking creates a majority of the braking force. Some hybrid drivers even find that, once they get the hang of it, they can drive most of the time by only using the accelerator! (Of course, everyone needs to hit the brakes once in a while, especially when coming to a complete stop.)

Energy Flow In/Out of the Battery

Drivers can see first-hand the fuel economy and energy flow distributed throughout the hybrid. From first starting up the vehicle to cruising down the highway, the computer system identifies which of the various driving modes it should operate in and adjusts accordingly. This could include gas-only mode, electric-only mode, idle mode or charging mode. Many manufacturers will showcase these energy flows in real-time – either in the instrument cluster or on the center screen. Each automaker has specific configurations, depending on the vehicle, that will engage and disengage when energy flows into or out of the battery. Understanding why and when your battery is charging up or sending energy to the wheels can be pretty interesting! And knowing when you’re using more of that precious battery power helps many drivers ease up on that gas pedal in order to be a little more eco-friendly.

Series vs. Parallel Hybrids

The term “drivetrain” is used to describe how power is delivered to the wheels in any type of car. With a gasoline drivetrain, acceleration requires fuel. That fuel comes from one source – the gas tank. In hybrids, it’s not so simple. Drivetrain design is important in hybrids because it determines how the vehicle’s mechanical components work with the various electrical systems to ensure the vehicle operates efficiently.

The purpose of a hybrid drivetrain is to conserve fuel without sacrificing performance. To achieve this, hybrids use an onboard computer that determines how much power comes from the battery, the gas engine and when. In HEVs, there are two primary drivetrains used: series and parallel.

Let’s explore each in more detail:

The series hybrid configuration is not as complex. There is an electric motor and a gasoline engine. When power is needed to move the wheels, the electric motor (and ONLY the electric motor) supplies the energy. The electric motor can use power from the battery pack or from a generator run by the gasoline engine, but not both. Think about the name series: one, then the other. Makes sense, right?

So, if the battery is fully charged, the car might opt to use the battery’s energy first. When the battery is nearly depleted, the vehicle will switch on the gasoline motor to generate additional power to keep the electric motor going. The transition from one energy source to the other is designed to be seamless.

Below, we’ve outlined the advantages and disadvantages of a series hybrid:

Advantages:

  • Battery pack provides majority of the power
  • Ideal for urban and suburban driving
  • Gasoline engines are smaller and more efficient than conventional

Disadvantages:

  • Costly to purchase as it requires a larger battery
  • Not as efficient when driving longer routes or for highway driving

Vehicle examples:

  • Chevrolet Volt, Honda Insight, Hyundai Ioniq, BMW i3 w/ Range Extender

Unlike series hybrid drivetrains (where only the electric motor can drive the wheels and the gasoline engine really only serves as its backup generator), a parallel drivetrain can put power to the pavement through the electric motor or the gas engine directly. An onboard computer will determine which is best for the given set of circumstances and make the choice for the driver.

Since there are two motors, they can work side by side to propel the car. This enables the onboard computer to continually monitor the need for acceleration and decide which motor (electric or gasoline) would be best.

For example, if you’re already moving but need a boost of power, like merging onto the freeway and getting up to speed, a parallel hybrid might put the gas motor to work. But when you’re sitting at a red light and it turns green, the same car might opt for the electric motor and its readily available torque, to get you from 0-30 mph ASAP. Plus, when the gas motor isn’t being used directly for putting power to the wheels, it will turn on to act as a generator for battery charging when needed.

There is also the concept of a Series/Parallel Hybrid which allows the electric motor and gasoline engine to drive the wheels simultaneously. This type of hybrid is discussed below when we cover the Prius.

Here are the advantages and disadvantages we’ve outlined for the parallel hybrid:

Advantages:

  • Engine and electric motor can directly supply torque to the wheels at the same time
  • Gasoline engine is less compact than those used in series hybrids

Disadvantages:

  • Complex structure can be complicated to repair
  • Not as efficient when driving locally – for example, stop-and-go traffic

Vehicle examples:

  • Audi Q8, Chevrolet Malibu Hybrid, Honda Accord Hybrid

The Series/Parallel Hybrid & the Dawn of the Prius

Prius is derived from the Latin word Primus, meaning “first.” The Toyota Prius has certainly lived up to the name. It was the first mass-produced hybrid. It also is somewhat unique because it was the first vehicle to combine series and parallel drivetrains, meaning it can be powered by the gas engine or the electric motor, or by both simultaneously. This is sometimes referred to as a “series/parallel” hybrid – which if you think about it, is like a hybrid within a hybrid!  

This power split is possible because of the planetary gear that was introduced in the second-generation Prius. Without getting too technical, the electric motor is attached to a gearbox that connects the gasoline engine, electric motor and generator together into one unit. The gear moves based on the power required by the car. The engine is the last of the gears, so initially the electric motor and generator run as long as possible; it is only when the two are unable to meet power demands that the gasoline engine starts up.

With more than 4.4 million Prius vehicles sold as of 2019, the Prius has continued to dominate the hybrid market. However, there is trouble ahead as electric vehicles continue to increase in popularity due to reduced complexity, cost and carbon footprint. Next, let’s explore how HEVs are different from electric cars.

What is the Difference Between Hybrid and Electric Cars?

The main difference between a standard hybrid and an electric car is that a hybrid car derives some of its power from a non-electric power source, like gasoline. Electric cars like the Nissan Leaf, Ford Focus Electric, or Tesla models run solely on electricity. Once the battery is depleted, an electric car needs to be recharged either at home or a charging station. With most hybrids, you can fill up with gasoline to complete your journey.

For the big picture on fully electric cars (also known as Battery Electric Vehicles, BEVs or EVs for short), please go to the section on Complete Guide to Electric Cars.

Similar Technology

The electric car is referred to as an Electric Vehicle (EV), Battery Electric Vehicle (BEV) or Zero Emission Vehicle (ZEV). For the purpose of this article, we will refer to electric vehicles simply as EV.

Similar technologies shared by hybrids and EVs include the battery technology and regenerative braking. The difference is that hybrids have reduced battery range and size compared to EVs. This is by design, as power is supplemented by the internal combustion engine for hybrid vehicles. EVs, however, need to be plugged in to recharge.

Regenerative charging provides power for both EVs and hybrids, but its effectiveness depends on the vehicle and conditions. For example, during winter, regenerative braking is slightly less efficient than during the summer. On average, energy recapture is anywhere between 10 and 27%. To learn more about batteries, check out our guide on Batteries/Range: Complete Guide to Electric Car Range & Batteries.

Not All Hybrids Can Be Charged

Unless it’s specified to be a PHEV, hybrids like the original Prius cannot be plugged into an electric source for charging. Bypassing the need to plug-in to recharge makes HEVs great for drivers who want the efficiency of reducing gasoline consumption without relying on charging equipment. Drivers who live in apartment buildings or businesses that deliver in urban areas can also benefit from the hassle-free efficiency of an HEV.

Note that a PHEV doesn't need to be charged either, as you can drive PHEVs 100% on gasoline; however, that would negate the fuel savings derived from using electricity as fuel. To learn more about PHEVs, please visit our guide on Plug-In Hybrids: Complete Guide to Plug-In Hybrid Cars.

Cost to Maintain

Many automakers have introduced hybrids over the years, with reliable models that require little maintenance outside the scope of what a gasoline car would need. This includes traditional maintenance such as tire change, oil change, coolant replacement, etc.

There can be slightly increased costs when maintenance involves the battery, oxygen sensors or evaporative emissions systems that are not working properly. While these issues are not common occurrences, it is important to note that the added complexity of a hybrid system can require a more specialized technician and, as a result, can increase the cost for some repairs.

EVs, on the other hand, cost less to maintain than a gasoline car or a hybrid because there are fewer moving engine parts. No oil to change, transmission fluid to replace, or timing belts to wear down. These added benefits can have a positive impact on your total cost of ownership.

Is a Hybrid Right for You?

The answer depends on your driving habits. If your commute allows you to make short trips in urban traffic, the battery in a PHEV or an HEV with series drivetrain will provide most of the power needed. If your commute involves lots of highway driving, a hybrid using a parallel or series/parallel drivetrain could work best for you. And while the latter won’t reduce your gasoline consumption completely, it would still provide a fuel savings over a conventional gasoline car.

In short, a hybrid will reduce your fueling costs, whereas an EV will eliminate the traditional fuel costs. However, both will reduce your carbon footprint.

A hybrid can be a great investment. Though it might be a little more expensive to buy upfront, when you look at total cost of ownership (reduced fuel charges, less maintenance, etc.), the savings over time will begin to add up. For the same reasons, EVs are able to offer even more savings over time. To learn more about EVs, please visit our guide Electric Cars: Complete Guide to Electric Cars.