Electric car fans love the fact that gas stations are everywhere. It gives them plenty of chances to thumb their noses as they glide past in silence. They may enjoy their smug little ritual, but they're in the minority. The fact is, electric cars aren't very realistic for most people. They may get you to work and help you run a few errands, but their limited range means keeping a second gas-powered car around just in case.
The answer to this problem? Plug-in hybrids like the 2011 Chevrolet Volt and 2010 Toyota Prius PHV (plug-in hybrid vehicle). They combine two systems into one. They'll run on electricity when they can get it and keep on truckin' on gasoline, sans leash, when the batteries are spent.
But we must warn you; it takes more than the usual number-crunching to sort out what's what. When it comes to comparing plug-in hybrids like the Volt and the plug-in Prius, you can't merely focus on the gasoline side and assume the electricity is free.
The Real Cost of Plug-In Hybrids
We can measure what it takes to fill a battery just like we can write down the numbers at the gas pump. With that in mind, we tested each car's all-important electric range and the cost to refill their batteries. We used both the garden-variety 120-volt "level 1" wall outlets and fancy-pants 240-volt "level 2" chargers.
And when the juice ran out we kept on driving. Not just anywhere, though. We measured their gasoline fuel-efficiency by running a carefully calculated driving loop that was representative of typical driving.
We did this because observed electricity and gasoline consumption is a crucial missing piece of the puzzle and because, frankly, we're geeks like that. But if you're someone who's not so interested in all those hard-to-understand numbers, you might not be Chevy Volt or Toyota Prius PHV material.
A Close Call
Here's a simple number for the less mathematically inclined: 0.6. In the end, the 2011 Chevy Volt and 2010 Toyota Prius PHV ended up less than one point apart — a virtual dead heat. But they arrived here along very different paths and they're not near as much alike as their close finish suggests.
At first glance, the basic ingredients of a Volt and a plug-in Prius seem identical. Each has a four-cylinder gasoline engine. Each has two electric motors (motor-generators, to be precise) — a larger one that handles most electric propulsion and regenerative braking chores, and a somewhat smaller one that helps out around the house by starting the gas engine, adding additional electronic boost, regulating speed or generating electric power with the engine.
Planetary gearsets in their transmissions blend these three elements into coordinated forward motion, a task that is overseen by complex computer software that makes continuous adjustments to the power flow mix in the name of maximum efficiency.
So far, this template describes most modern, fully realized hybrids. What set the Volt and Prius PHV apart are their batteries, which are greatly enlarged lithium-ion units sized well beyond the needs of mere regenerative braking.
The Prius PHV uses a battery rated at 5.2 kilowatt-hours (kWh), enough for 13-14 miles of electric range after a full charge. The Volt's battery, larger still at 16 kWh, was recently rated by the EPA at 35 miles of e-range.
Details Define Differences
Their mechanical similarities blur when we zoom in for a closer look. The 2010 Prius PHV's larger 80-horsepower (60 kilowatts) electric motor is tasked with powering the front wheels. But as its efficiency wanes at 65 mph or so, the 98-hp 1.8-liter Atkinson-cycle gasoline engine fires up to help out. No clutches, gear-shifting or hydraulics are involved — it's all done seamlessly with constantly enmeshed planetary gears.
Such gasoline-fueled assistance can happen even with a full battery in electric vehicle (EV) mode, and the road speed at which the engine engages is lower when we stab the throttle or climb a hill. Drivers expecting a pure EV experience may be confused when the engine cycles on in such situations, though it turns out this expectation is largely symbolic and unimportant, as we'll see later.
Like the Prius, the Volt's main 149-hp (111-kw) drive motor powers the front wheels, though the route to get there differs. Similarly, its efficiency trails off at around 65-70 mph, lower still when driver demand is high. But here it's the secondary electric motor that clutches in to assist the main motor, while the 84-hp 1.4-liter gas engine remains dormant and de-clutched from the system. That's right; the Voltec system employs clutches, three in all.
This is the status quo until the battery runs down, at which point the Volt's gas engine begins driving the secondary motor to generate electricity for the main electric motor, which continues to drive the car. At higher speeds or high demand, the internal combustion engine itself is ultimately clutched in to mechanically assist with propulsion while, with its other hand, it continues to generate power for the primary electric motor.
Battery of Tests
The EPA recently released official ratings for the 2011 Chevrolet Volt. Its gasoline fuel economy is listed at 37 mpg, electricity consumption is 36 kwh per 100 miles and 35 miles is the official electric range. But this is of little use here because no comparable EPA figures exist for the Prius PHV plug-in.
That's OK. We ran our own test loops instead. The numbers may not match perfectly, but each car was driven the same way on the same courses, so the data is at least comparable one to the other, which is why we're here.
We measured gasoline mpg by driving test loops with a discharged battery — pretty standard stuff. But we also measured electricity consumption by driving a known distance and then using a special meter to determine how many kilowatt-hours of juice passed through the charge cord during the subsequent battery recharge.
After crunching the data, here are the Edmunds Observed figures we came up with:
EV-mode electricity consumption (*kWh/100 miles) *unlike mpg, smaller is better:
Prius PHV 23.2
HV-mode (hybrid vehicle) gasoline fuel economy (mpg):
Prius PHV 47.2
EV-mode electric range (miles):
Prius PHV 14.6
Driven the same way, our Prius PHV used 34 percent less gasoline in gasoline-hybrid mode and 41 percent less electricity in EV mode than the Volt.
Utility Factor and the Bottom Line
Several editors live more than 50 miles from the office, so they view the plug-in hybrids through the lens of their lengthy 100-plus-mile round-trip commutes. Conversely, GM likes to focus on the Volt's prowess as an electric vehicle, which it can be, sometimes, but certainly not all the time.
So if these aren't EVs 100 percent of the time, then what fraction of an EV are these plug-ins hybrids? Fortunately, the Society of Automotive Engineers has developed something called the Utility Factor (UF) to pin this down. Don't think of UF as a measurement of usefulness; the word "Utility" here refers to "electric utilities" and the percentage of total driven miles that are expected to come from juice from the power grid.
Simply put, the UF concept states the obvious: The more electric range a plug-in hybrid has, the more miles it will cover as an EV during its lifetime. The UF concept is math and statistics-based, but it boils down to a pretty graph and some equations.
For the Volt, the graph tells us that 33.9 miles of observed range makes it an electric car 57 percent of the time, while the Prius PHV's 14.6-mile range translates to a 31 percent UF. These are the weightings we'll use when blending electricity and gasoline costs to get to a bottom line.
For the first year, the Chevy Volt will be sold on a limited basis. So instead of using the national average prices for electricity and gasoline, we averaged the prices charged (as of this writing) in the places that will sell the 2011 Volt: California; Connecticut; Michigan; New Jersey; New York; Texas; and Washington, D.C.
Electricity: 15.8 cents per kilowatt hour
Gasoline: $2.96 for regular and $3.25 for premium (required in the Volt)
Assuming a 15,000-mile driving year — 1,250 miles per month — we distilled our measured consumption rates and their UFs down to a single monthly fuel cost:
2011 Chevrolet Volt $99.87
2010 Toyota Prius PHV $68.24
Here's another way to look at this: If you had the same amount of money to spend on a normal car's regular unleaded gasoline every month, what EPA combined mpg rating would that car have to achieve to cover the same 1,250 miles? This is what we like to call mpg-c, the cost-based mpg equivalent.
2011 Chevrolet Volt 37 mpg-c
2010 Toyota Prius PHV 54 mpg-c
You may notice that our 37 mpg-c number for the Volt differs quite a bit from the 60 mpg-e "combined composite" number that's found on the EPA label. That's largely because the EPA does not use cost as a basis for converting electricity consumption into mpg. Instead, it uses energy content to equate the two.
This is great for scientists, but gasoline and electricity are independent commodities that are not priced on an energy content basis, meaning the EPA's mpg-e unit is pretty much meaningless. Our mpg-c unit is far more useful if you're accustomed to using window sticker mpg as a cost yardstick.
How Do They Perform Anyway?
This was still a traditional comparison test, so we still track tested the two hybrids. The 2011 Chevy Volt has its way with the Prius PHV despite an extra 380 pounds of curb weight.
To conduct the test, each vehicle sat overnight while plugged in so testing could commence with maximum battery power. In the 2010 Prius PHV, this made no difference, because, as described earlier, the engine comes to life as soon as something like a wide-open launch is requested. The resulting "dash" to 60 mph took 10.1 seconds (9.8 with 1 foot of rollout as on a drag strip), with the quarter-mile finishing in 17.4 seconds at 79.1 mph, on par with the last regular 2010 Prius we tested.
We first ran the Volt on pure electrons, but it ended up going faster after our lackey drove it around until the batteries ran down and the engine lit up. This bought us 0.2 second and a full 4 mph of trap speed, as the dino-fed Volt reached 60 mph in 9.0 seconds (8.6 with rollout) and reached the quarter-mile in 16.6 seconds at 85.5 mph.
On the skid pad the Volt eked out a slight victory worthy of no more than a golf clap, pulling 0.77g to the Prius' 0.75g effort. But the Prius lagged even further behind through the slalom, managing just 57.6 mph in a weak effort that made the Volt's ho-hum 60.2-mph pass look scintillating.
The Volt's 124-foot stop from 60 mph looked vulnerable to attack because the last Prius we tested did the trick in just 118 feet. But this Prius PHV weighs 300 pounds more than that car and rides on the same skinny P195/65R15 rubber, so stopping required 130 feet this time.
Taking Them to the Street
You can almost see how differently these two behave by studying them from 20 paces, even though they both ride on similar underpinnings: MacPherson struts in front and a twist-beam axle in back.
Sitting 2.4 inches lower, 2.1 inches wider and riding on wider P215/55R17 tires, the Chevy Volt feels planted in real-world corners and steady on straight highway sections. The electric power steering isn't particularly communicative, but it is livelier than the Prius.
The overriding impression of a well-sorted family/commuter car is further bolstered by a smooth ride that's admirably quiet, at least until the battery runs down and the engine fires up. Even then, the Volt's cabin has better overall isolation.
But in city traffic and on hilly terrain the engine sometimes stands out when it revs higher than expected — 2,000 rpm or thereabouts, oftentimes when coasting — as it seeks to bank electrons in anticipation of the next acceleration. There's also a low-level thrum at highway speeds that makes us wonder if we're feeling that secondary motor at work.
Our Prius, on the other hand, feels less substantial, more nervous and up on its tiptoes, especially on higher-speed roadways. It looks taller and skinnier, and that's pretty much how it drives. Light doesn't begin to describe the steering.
It isn't terribly quiet either, as the Prius Hybrid Synergy Drive system emits a Rube Goldberg sampler platter of whirs, moans and clicks as it goes about its business. Hybrid fans may excuse these as endearing quirks that prove it's doing something, but we bet they'd prefer silence.
The Volt's color-screen instrument panel is attractive and useful, but we can say only half as much of the gleaming white center stack. Its touch-sensitive surface is a technical success, but the mass of same-size and evenly spaced buttons are hard to distinguish from one another. After all, some of us have been typing for a couple of decades yet we still have to hunt for the desired key.
Our longstanding dislike of the Prius' center-mounted gauge cluster need not be repeated here, and we still think the shifter's Park position should not be a stand-alone button. But at least the spacey-looking center stack is easy to use, with clearly labeled buttons grouped by function.
Both cars have ample head- and legroom up front, but our drivers give the clear nod to the Volt, based on driving position, shoulder room and a more-generous telescopic steering column.
But the Prius' high roof line and slightly longer wheelbase gives it a spacious backseat and generous cargo area (20.4 cubic feet to the Volt's 10.6), which explains why they're popular as taxis. Our taller testers griped about a lack of knee- and headroom in the Volt's backseat, so we doubt many will wind up in the hands of cabbies.
Furthermore, the Volt only seats four because its T-shaped battery passes between the two rear seats. The necessary rear buckets are comfy and the open slot back to the hatch is a cool look, but it's not exactly practical, as there's no continuous wall to keep luggage and road noise from spilling through the gap.
How Much Do They Cost Anyway?
Our 2011 Chevrolet Volt starts at $41,000, including destination charges. Navigation is standard here, but the leather seats, rear back-up camera and the polished finish on its forged aluminum wheels bring the total up to $43,685.
But the size of the Volt's battery, 16 kWh, qualifies it for the maximum federal tax credit of $7,500, which brings the effective price down to $36,185. Better, but still a good chunk of change.
We had to estimate the price of our 2010 Toyota Prius plug-in because, technically, it's a demonstration vehicle that's not really for sale. Based on Toyota ballpark estimates for the PHV system, we used current Prius prices and made an upward adjustment of $4,000. That brings the base price up to $28,560, but in Priusland the navigation system is optional so our estimated as-tested price climbs to $30,590.
A Prius PHV would also be eligible for federal support, but its smaller 5.2 kWh battery limits the credit to $2,917. Still, its theoretical price drops to $27,673, some $8,500 less than the Volt.
But Chevrolet only plans to sell 10,000 Volts this first year, and there are probably more than enough well-heeled early adopters itching to snatch them up, even at this price. Besides, you can't actually save that $8,500 by buying a 2010 Prius PHV because they're not actually for sale.
We Already Smell a Rematch
The fact that the plug-in Prius doesn't really exist yet is the tiebreaker that cements the win for the 2011 Chevrolet Volt. It's a plug-in hybrid, and conceptually that's a good thing. If your commute is short and your foot is light, you may be able to beat the UF prediction and spend much more time in EV mode. And, more than anything, the 2011 Chevrolet Volt is in production and available for sale right now.
And we expect further enhancements to the Volt as early as the 2012 model. That iron-block 1.4-liter engine and its thirst for premium fuel would be a good place to start. A change here would do much to improve the bottom line.
Toyota tells us the Prius PHV will come to market, but not until late 2012, some two years hence. When it does arrive, we expect it to be a 2013 model. Toyota also suggests the car it will sell will contain lessons learned from this pilot program, so expect it to be stronger in one or more respects.
A PHV's inherent lack of a "leash" and immunity to range anxiety is why, for many of us, plug-in hybrids rule and electric cars drool. And as it stands now, the 2011 Chevrolet Volt is the only game in town.
The manufacturers provided Edmunds these vehicles for the purposes of evaluation.
Engineering Editor Jason Kavanagh says:
Running cost is certainly an important metric when it comes to plug-in hybrids like the 2011 Chevrolet Volt and 2010 Toyota Prius PHV. But it's not the only consideration.
Various types of people will buy these cars. Initially it will be early adopters and enthusiasts (yes, even eco-weenies are a form of auto enthusiast) to which running cost is justification rather than a need. Longer term, these cars will have to play well with normal everyday consumers. These are the people to which these cars must pencil out, or these cars don't really make sense.
Yet among all the motivations a person has in buying a plug-in hybrid, there's one area of common ground — what's it like to drive. And that's where the Volt has a decided edge over the Prius. The Prius is quiet, yes, and has a spacious backseat and possibly the most soul-sucking driving experience of any modern car. No steering feel. Synthetic brakes. Turgid acceleration. Absolutely lifeless to drive.
It'd be easy to dismiss the above missive as talking points from the knuckle-dragging performance enthusiast's bible until you consider that cars that don't communicate with their driver do not inspire confidence. A confident driver is a safer driver, which is something that is relevant to all drivers and all roads. Capable cars are their own reward.
In no way is the Volt a sports car or even a sporty car, but at least it provides a modicum of heft to its steering, some alacrity in turning and a ride that provides a reassuring sense of substance. Those are the things that everyone can get behind whether they realize it consciously or not.