Should I Buy a Plug-in Hybrid?


chevy volt

2017 Chevy Volt

In short – probably not. Unless it’s a Chevy Volt. Why? Read on! (Update, Sept 12, 2017 – Honda announced their new Clarity plug-in which sounds like it will give the Chevy Volt a run for its money! Update, Sept 14: Maybe not. Driveability sounds so-so and based on this article, you only get 121hp in EV mode 😦  ).

Virtually every auto manufacturer has pledged to electrify their product lines before 2025. This could mean making all their cars hybrids, like the Prius. But many are mentioning at least some of those cars will be “plug-in” hybrids or fully electric vehicles.

In previous posts, I’ve discussed the great benefits of pure electric vehicles – great drivability, simplicity of drivetrain for minimal maintenance, zero exhaust pollution, and never having to go to the gas station. I’ve also written about the difference between the types of electrified vehicles, but I haven’t done a deep-dive into plug-in hybrids. In all likelihood, you’ll be seeing many vehicles with this label in dealer showrooms, but what exactly do they mean? Hopefully, by the time you finish reading this post, you’ll understand and be able to purchase your next vehicle, confidently knowing exactly what you’re getting.

Plug-in hybrids are hybrid vehicles with larger batteries and a switch that allows you to change them from gas-electric propulsion to electric only. “Great!” you might think – “best of both worlds! Now I don’t have to worry about the range of the batteries since I can always switch on the gas engine.” However, all is not so rosy. As with everything in life, there are compromises.

Prius prime

2017 Prius Prime

Step back for a moment – what is a hybrid vehicle? How does it work?

While the exact details vary, the concept for most hybrids is the same. They have both gas and electric motors, tied together through a complicated drivetrain. Some power comes from the electric motor(s), some from the gas engine. When you brake or slow down, some of the energy is stored in a battery. When you accelerate, the battery drives the electric motor(s) harder so the gas engine can run efficiently, doing little of the work. Here’s a diagram I borrowed from Toyota:

prius drivetrain

With a hybrid car, you never have to worry about plugging it in. In fact, when they first came out, they advertised this as a virtue – it’s an electric car you never have to plug in! No cords necessary!

What this means is that gasoline provides all the energy for the vehicle and the electric part is really just a mechanism for storing and using energy that would otherwise be wasted. For example, every time you hit the brakes in a normal car, the energy of braking is wasted as heat, wearing down the brake pads. In a hybrid, when you hit the brakes, the electric motors act as a generator, using that braking energy to charge the batteries. Then, when you accelerate, it releases some of that energy. The process makes the cars much more efficient in stop and go traffic. But basically, it’s just a more efficient gas car.

Now that electric cars have become fashionable, manufacturers are adding charging ports, allowing you to fill up those batteries at home. This indeed displaces some of the need for gasoline. But once you use up that charge, you’re back to burning gas. So the size of the battery pack makes a huge difference. This is why these vehicles have a “battery only range” as well as a total range. Keep in mind – almost all plug-in hybrids work like the Prius – gas and electric motors work together, in parallel, to drive the car. This is a critical point. Because they work together, each motor is smaller (i.e. less powerful) than if they had to work alone. This is why most hybrids don’t have spectacular acceleration. For those interested, here’s a page with the 0-60 acceleration times of many “green” vehicles.

This is particularly important if you plan on running the plug-in hybrid in “electric only” mode, as you would if you buy this type of car. The Toyota Prius Prime, their plug-in hybrid car, has a total power of 121 hp, with the gas engine producing a paltry 95 hp.

More telling is the acceleration: 10.9 seconds for 0-60. That’s pretty pokey. And that’s for the hybrid mode. Worse, when I searched, I found that the electric-only mode takes 15 seconds for 0-60. No Tesla-like, eye watering acceleration here! This is slower than the normal Prius hybrid that has a 0-60 time of 9.7 seconds. IMHO, 15 second acceleration in electric mode renders this vehicle virtually unusable. Earlier versions of the Toyota Prius plug-in had even worse acceleration, with one source quoting 27 seconds!

Why? The drivetrain is a (horrible) compromise, not designed for electric-only driving. It’s a hybrid with larger batteries and now it has to drag along another few hundred pounds of batteries, added to support plug-in mode. Since it’s designed for combined gas-electric driving, each individual engine is underpowered. The net result is unsatisfactory driving in electric only range. Worse, in some plug-in hybrids, you lose cargo space since those batteries have to go somewhere.

You might ask: “why do I need great acceleration if I’m just using electric mode for local errands?”

To some extent, this is true. You don’t need blistering acceleration, but you do want reasonable acceleration. To get a feel for this, you can look at 0-30 acceleration times. Most normal vehicles do this in 2.5 to 3.5 seconds. The latest Prius Prime does this in 3.5 seconds in EV mode. The Chevy Volt (mentioned below) does it in 2.5 seconds. For comparison, a Honda Civic takes 3.3, so you can drive the Prius Prime in EV mode, it will be pretty pokey, even at slow speeds. And definitely don’t try to zip into traffic, or you may find yourself in a pickle.

Enter the Series Hybrid

Thus far, I’ve been talking about the parallel hybrid design. Remember, the parallel hybrid has both the electric and gas motors running together, in parallel, to drive the wheels and propel the car. The series hybrid is a much simpler and more logical design.

In the series hybrid, the gas engine is only used as a generator to charge the batteries. The electric motor(s) drive the wheels. This has great advantages over the parallel hybrid design.

Firstly, gas engines have an efficiency curve, depending on load. This is why they burn so much fuel when you accelerate hard and are much more efficient when running steady, say cruising slowly on a highway. In a series hybrid, the gas engine can run at its optimal output, charging the batteries as efficiently as possible.

Second, since only the electric motors propel the car, the electric motors are the right size. That is, they are powerful by themselves, so you don’t give up any acceleration when running in electric only mode, since the only thing that happens in this mode is the gas generator is turned off.

Third, in a pure series hybrid, the drivetrain is simpler. There’s no complex gearing required to combine the outputs from two sets of motors. The gas runs a generator. The electric runs the wheels. Simple!

The net result of this is the series hybrid provides the drive/acceleration of an electric car regardless of whether the gas engine is on or off. In addition, because it can burn gas as needed to charge the batteries, you get more range than a battery only vehicle with the same size battery pack. And, you can stop at any gas station to top off the fuel tank, so you’re never stuck without a charge.

The BMW i3 Rex is probably the best example of a series hybrid. You can purchase the i3 in a pure EV model that goes about 125 miles on a charge or the Rex (Range extender) model that brings total travel up to 180 miles. This is actually pretty cool as the extender lies dormant until you’ve depleted the batteries, eliminating the range anxiety common with pure EVs. Acceleration is 6.8-7.4 seconds 0-60mph. (The 2018 model is the i3s that gets you the 6.8 second figure).

The Chevy Volt is an example of a quasi-series plug-in hybrid. It has a good acceleration of 7.5 seconds and a battery-only range of “up to” 53 miles, far greater than most plug-in hybrid’s ranges of about 20 miles. This means you can do virtually all your local driving in electric only mode. And if you charge it every night, under typical conditions, you’ll rarely have to add gasoline. Chevy says that most users travel over 1000 miles between gas fill-ups.

However, the Volt is not a “pure” series hybrid, as described in this article by Green Car Reports. While they do use just the electric motor when running in EV mode, they actually have a complex gearing system to combine gas engine with electric motor when running in hybrid mode, providing more power and acceleration.

Why more manufacturers haven’t released series plug-in hybrids is beyond me. Maybe it’s lack of foresight or the time simply hasn’t been right (high battery costs, etc.). But for me, if I were looking for a vehicle for a single-car household, the Chevy Volt would be just the ticket. My only hesitation with the Volt is it’s relatively small cargo capacity. Otherwise, it’s an awesome vehicle.

Update: Sept 12, 2017 – Honda just announced their Clarity plug-in and it sounds very nice. 47 miles of all-electric range with an MPGe rating of 110, almost matching the Chevy Volt. Plus, it has a 181 horsepower electric motor making it the most powerful plug-in hybrid on the market (almost), so it’s going to be zippier than most plug-in hybrids. Unfortunately, based on this article, only 121 of those horses is available in EV mode. Foiled! Not a Tesla by any means, but for a plug-in hybrid, it’s going to be a lot more fun to drive than the others.

Another variation

A unique configuration that I expect to see in more vehicles is that of the Mini Countryman ALL4, released in 2017.

This ingenious car uses the gasoline engine to drive the front wheels while the electric motor powers the rear wheels. In this way, it can provide all-wheel-drive, something few plug-in vehicles do. I find this quite compelling as it allows using it in efficient EV mode during the non-snowy seasons, when the batteries are most efficient and hybrid AWD mode in the winter, when you need AWD and want the range of a gasoline engine. And with two motors driving the wheels, it does 0-60 in 6.7 seconds. This is a zippy little car.

Unfortunately, the range and fuel efficiency of the mini is horrible in comparison to other vehicles in this class! The electric-only range is 12 miles – probably barely adequate for going to the grocery store and back. The combined city/hwy MPG is only 27. And the MPGe is 65, compared to roughly 100-130 for most other plug-ins. The Volt gets 133 MPGe for comparison. The total range of the car is only 270 miles, so you’ll be filling up often on road trips.

So while amazing in theory, in practice, they’ve created a real dud.

What to look for when buying a plug-in hybrid

Now that you understand some of the possible shortcomings of plug-in hybrids, what should you look for when shopping for one?

Battery-only range

This is the primary figure that will determine how useful the plug-in mode will be. Some plug-ins have very small batteries that you’ll deplete quickly. If a vehicle has less than about 15 miles of range, you may want to cross it off your list. Most of the modern plug-in hybrids will give you about 20 miles of range. Good enough for most shopping trips but probably not enough for a daily commute. With 20 miles of range, you’ll find that you have to fill up at the gas station less frequently, but still enough that it won’t feel like the car is saving you that time. The Chevy Volt is at the top of its class, with more than 50 miles of range. This is getting into the realm or true usefulness!

For comparison, I am currently driving an e-Golf (a pure electric vehicle) that provides about 90-100 miles of battery only range. On average, I fill it up about every three days, though I almost never run the battery down too low. I want to keep it at about 90% full every morning so I can take any local trips without worrying about running out of battery. On most days, my errands are within that 20 mile range. Then I’m home and could plug it in to top it off before my next trip. However, I do think that I’d find even 20 miles to make it hardly worth the added expense of a plug-in hybrid.

Combined battery and EV range (total range)

The total range of the car is another important spec. Most buyers of plug-in hybrids purchase them for two reasons: 1) they want to be able to drive in EV mode for local errands; 2) they want to be able to drive long distances in hybrid mode.

Most plug-in hybrids try to equal gas-only vehicles, providing 350-450 miles on a fill-up. They come to this figure by combining the gas range and the electric range. Often this allows them to use a smaller gas tank than a normal vehicle. For example, the Chevy Volt is spec’d to have a 420 mile total range. Since it gets about 50 miles from its batteries, you’d get about 370 miles from gas. This should be fine for most road trips.

However, there are some bizarre plug-in vehicles, like the BMW i3 which doesn’t know what it wants to be. It’s designed to be used as a pure EV, giving around 125 miles per charge. But they also include a “range extender”, which is a gas generator with a tiny 2.4 gallon tank (in the latest model), giving about 180 miles of range. This is a pure series hybrid, taken to absurdity. You’re paying the premium price of a battery electric vehicle then strapping a gas engine on it for those times you run out of battery or want to drive more than 100 miles in a day. But with such a small battery, it still isn’t really suitable for long road trips. They should have just given it a 10 gallon tank, allowing it to drive 400 miles on a fill-up, but they were playing games so as to qualify for California’s EV program. OTOH, it eliminates the range anxiety one might feel with a pure EV since you know you could always get to a gas station. But I still wouldn’t drive it on a 400 mile road trip unless absolutely necessary!

Battery-only acceleration

We’ve already discussed this at length, but you have to decide for yourself if the acceleration is good enough for your purposes. Numbers tell you one thing but you really need to test drive the car in EV mode to get a feel for it. Most importantly, can you safely pull into traffic in EV mode using your normal driving habits. I can’t stress this enough. You don’t want to be having to remember which mode you’re driving in and adjusting your driving – that’s a sure recipe for an accident. If the car feels fine in EV mode, then great. If you feel like you’re going to have to consciously adjust your driving for EV mode, I would seriously doubt whether you’d be happy with the car.

Handling

During your test drive, you may want to test out the handling of the car. You’d do this for any vehicle, but it’s particularly important for a plug-in hybrid. These cars carry a substantial battery pack, often weighing hundreds of pounds. This can be like adding a couple of passengers, making the car feel slow to respond or roll more in corners. OTOH, some cars take advantage of this extra weight by mounting the batteries down low on the chassis which improves the handling. Though it will still be carrying extra weight, so the brakes have to be beefed up for effective stopping power.

Summary

Overall, I see most plug-in hybrids as a stopgap solution, designed for a time when batteries are too expensive to provide enough range and people want to drive a vehicle without using gasoline. For that purpose, they fill a useful niche. Most plug-in hybrids provide enough battery range for around-town errands, and enhanced hybrid-mode gas mileage. Combine that with the ability to take a full-length road trip, and you have a car that might just be good enough to be your daily driver. But with the benefits, there are definite disadvantages. The more complex drive train could spell more long term repairs. And the small electric motors in most provide poor acceleration, inadequate for most highway driving.

In general, if you want to dip your feet in the EV world, you could do worse than getting a plug-in hybrid. But if you want the true EV experience, you’re best off with a battery only car. Or, you could get a Chevy Volt and get an excellent hybrid combined with a pretty good electric vehicle.

References

Plug In America – trade group for plug-in vehicles. Includes specifications for many currently available cars

My spreadsheet of EVs, Plug-ins and Hybrids – A handy spreadsheet I made while searching for utility electric vehicles. I focus on compact SUVs and hatchbacks though include others for comparison purposes.

 

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2 thoughts on “Should I Buy a Plug-in Hybrid?

    • Thanks Jim. It’s funny. For years, I thought the plug-in hybrid would be the best of both worlds. Then I started looking into buying one and only then did I realize that, in many cases, they weren’t at all what I thought! They were just normal hybrids with enlarged batteries, leading to them being mostly useless as EV replacements.
      As they say, “caveat emptor” (buyer beware!)

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