2010 Toyota Prius Plug-In Hybrid Prototype: Drive Report

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The main thing to understand about the Toyota Prius Plug-In Hybrid is that it's not an "electric car" as many people use the term.

Yes, it plugs in to any electric socket to recharge the 5.2-kilowatt-hour lithium-ion battery pack. And, yes, its Hybrid Synergy Drive system uses electric torque, either by itself or along with the gasoline engine, to turn the front wheels.

But in a four-day test drive over the long holiday weekend, we came to understand one fact clearly: The plug-in Prius is not an electric car in the same sense as the 2011 Nissan Leaf and or the 2011 Chevy Volt.

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

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Still mostly gasoline

While it travels further just on electric power than a standard 2011 Prius, and can do so at higher speeds, the gasoline engine still provides most of the torque to propel the car in mixed duty cycles.

Over 424 miles, we plugged in the car to recharge the pack six times. (A 22-foot-long cable for 120-Volt charging is provided in a bag in the load bay.) Not all of those periods lasted 3 hours, which meant that twice, the pack was only partially recharged.

We were able to run locally on electric power for a few short trips--especially the downhill ones (our house is toward the end of a mountain path several hundred feet above valley level).

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

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Northeastern autumn

But the exterior temperatures of a Northeastern autumn (25 to 40 degrees F), as well as a duty cycle with almost half the miles on Interstates, cut heavily into the car's ideal electric operating range.

Bottom line? Over our entire test, the Toyota Prius Plug-In Hybrid averaged 53.9 miles per gallon.

That's better than the standard 2011 Toyota Prius hybrid, which the EPA rates at 51 mpg city, 48 mpg highway, for a blended average of exactly 50 mpg. In practice, most drivers of third-generation Priuses seem to get in the mid- to high 40s.

But the Prius Plug-In's mileage was lower than the Volt's blended 60-mpg rating under the EPA's standard test assumptions, let alone the Nissan Leaf's slightly ludicrous "99 MPGe" rating (for a car that uses no gasoline at all).

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

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EV mode: 8 percent

And over a longer 777-mile average (which we retained in the Prius Plug-In's trip computer for comparison), the car operated in EV Mode just 8 percent of the time, and a whopping 92 percent as a standard hybrid.

That can be viewed two ways. It's an endorsement of the fundamental efficiency of Toyota's Hybrid Synergy Drive system, but it's also an indication that the Prius Plug-In's small battery pack only expands incrementally on the standard Prius electric-drive capabilities.

Our recent results also underscore the contrast with our April first test drive of the Prius Plug-In Hybrid, which took place in temperate San Diego.

There, on a 10-mile test route that included low-speed city driving, a 3-mile section of freeway where we hit 86 miles per hour, and a few hills, we obtained "99.9 mpg" and spent 63 percent of our time in EV Mode.

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

prototype 2012 Toyota Prius Plug-In Hybrid, April 2010

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50 to 70 percent of EV range

Over Thanksgiving, in contrast, we achieved between 6 and 10 miles on stated electric ranges of 12.9 to 13.5 miles from a fully charged battery. And after sitting overnight in the cold, the engine switched on as soon as we powered up the car.

To maximize electric range, we used the front seat heaters but not the cabin heater, and accelerated gently. Nonetheless, the battery provided significantly less range in cold weather than it had in San Diego.

Once the EV mode switched off, the Prius Plug-In Hybrid reverted to being a standard Prius with about 100 extra pounds. Our car exhibited a few prototype aspects, including a relay that clicked whenever the brake pedal was pushed or lifted, and a trim buzz under the dash.

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Comments (10)
  1. I'd like to see two more tests please, an easy one and a tricky one;
    The first: I'd like to test a Prius with all batteries disconnected. With its efficient engine, body and low rolling resistance tires, transmission, etc. I suspect that it'll turn in a sound mpg rating without the hybrid components answering the question "How useful is the hybrid tech?"
    The second, a little more tricky to do; put that nice Tesla power-train into the Prius and pop out the oily bits; wouldn't take more than a long afternoon? What would an EV Prius be like; quite a nice motor I suspect. Leaf competitor?

  2. What is a "load bay?"

  3. @Michael: The area behind the rear seats that is accessed via the hatchback or, with the rear seats folded down, via either rear door or the hatch.

  4. @Michael: Remember that full hybrids like the Prius use Atkinson cycle engines that have close to zero torque low down in their range. They are tuned to use the battery-powered electric motor to provide low-end torque during high power demand until the engine speeds up enough to generate torque.
    I suspect a Prius minus the battery would be undriveable. As for your second test, see the Toyota-Tesla RAV4 EV project ... :)

  5. "Ah Prius drivers endless source of entertainment."
    Thanks for the review here. It does seem like the Prius is neither "fish nor fowl". Not the beauty of a full EV or the classic experience of an ICE car.
    I guess, as you say, Toyota's only move is to price the plug-in Prius such that people who are going to buy a Prius anyway, will buy the plug-in one.
    A couple of years ago, there was a lot of noise from GM saying that second generation Volts would have smaller (cheaper) batteries with less range, say 20 miles or 10 miles. This was contrary to expectations of the EV community that wanted to see an 80 mile range Volt.
    If a lower range Volt comes to pass, the plug-in Prius will be much closer to the Volt, however, it may still lack the elegance of the series (ish) hybrid.
    John C. Briggs

  6. Thanks for the review! One can only wonder what the plugin Prius could do if the battery pack was say, 12-16kWh, and/or if the larger battery could be (re)charged with the regenerative braking? And why is the Prius capable of getting ~20MPG better than the Volt? It is considerably larger, and has about half (?) the usable battery capacity.
    If Toyota chose to put a 2-3X larger battery in the plugin Prius, they would certainly beat the Volt handily.
    Sincerely, Neil

  7. Neil,
    For one thing, the Prius is 2900 pounds and the Volt is 3800 pounds.
    John C. Briggs

  8. Neil,
    For one thing, the Prius is 2900 pounds and the Volt is 3800 pounds.
    John C. Briggs

  9. Neil...we need not wonder, as you know, I have a 12KWh (officially a 10KWh) PHEV Prius, Converted by PlugInSupply...works for me...Some numbers: 49mi pure electric range on the flat, I average 80-90mpg on my hilly highway commute.

  10. Toyota would be smart to offer a larger lithium barrery, extra 5 kWh or more doubling battery capaciuty, as an option (dealer installable)on the plug-in prius. If done right it would double the electric range and double the Federal Tax credit. Repackaging the existing battery pack to fit trunk and a few software fixes should be easy. Maybe a cooperative dealer could do it.

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