PHEV Letdown Begins

Edward Niedermeyer
by Edward Niedermeyer
phev letdown begins

Danny Westneat at the Seattle Times apparently wasn’t taken in by the “This Car Gets 100/150MPG!” signage on Seattle’s test fleet of plug-in hybrid electric vehicles (PHEVs). And it seems that his journalistic incredulity was rewarded with some disappointing numbers from Seattle’s real-world testing of the much-vaunted PHEVs. Sure, a converted plug-in Prius might get 100 mpg in the hands of a fanatic hypermiler, but in daily use by untrained city drivers, the PHEVs return much more moderate results. Westneat reveals that Seattle’s 14 plug-in Priuses actually averaged about 51 mpg after driving a total of 17,636 miles in all kinds of conditions. And the Seattle case is no fluke.

Google’s “Recharge” fleet of PHEVs returns similarly underwhelming results on average, specifically 37.7 mpg from a plug-in Ford Escape and 54.9 mpg from several plug-in Priora. Now, clearly 37-55 mpg is an improvement over their standard hybrid equivalents, but with Prius PHEV upgrades retailing fom $10K and up the cost of plugging in works out to around $1K per mpg improvement. According to Westneat’s math, even if battery prices were cut in half PHEV Priora would have to hit 80-100 mpg to overcome the shocking plug-in premium. And that’s not great. Are PHEV’s evolving technology? Sure. Will changes in driving style help improve those numbers? Probably. But does slapping “This Car Gets 100 MPG) on the side help the cause when those numbers don’t translate to reality? Not so much.

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4 of 22 comments
  • Niky Niky on Feb 24, 2009

    3 mph isn't hypermiling. It's wasting gasoline. You want to get up to 20 mph, then shut off the engine and coast. ;) 51 mpg... plus the cost of electricity? Dear lord, I nearly choked when I read that line. Here's a thought. Why don't we chuck out the insanely expensive hybrid drivetrain and run the whole thing on electricity? I can get 50 mpg in a diesel. And before anyone interjects to say "clean", the amount of fuel you use is directly related to CO2. Anything getting 50 mpg is emitting the same amount of CO2. No, wait. If that's 50 mpg plus electricity, that's 50 mpg's worth of carbon emissions plus whatever emissions are generated to generate and transmit the electricity used.

  • Stevelovescars Stevelovescars on Feb 24, 2009

    I'm no expert on these conversions, but I would have to think that this test isn't representative of what a purpose-built PHEV can really do. For one thing, the converted Prius still only goes up to about 35 mph on electric propulsion only... and that's likely only in a situation in which a driver is driving conservatively. Given the driving habits of a bunch of government drivers who aren't paying for their own gas it's unlikely they were getting the best efficiency. A series-hybrid plug-in, on the other hand, can theoretically go faster on electric propulsion, thus making the first 30 miles or so of daily driving gasoline free. Of course, one still has the added weight and complexity of the two systems and batteries vs. a pure battery-only EV. I would think that the most efficient would be a pure plug in optimized for commuter duty and a second light-weight efficient gasoline or better, Diesel-powered vehicle for the occasional longer trip. In my household, my wife and I each have our own cars... hers a Mazda5 used for family trips and kid-hauling duty. My car (a 1994 mid-sized Mercedes convertible) is usually relegated to local commutes, driving my son to school, and local errands. Like many families, I bet I could make due with one of these cars as a plug-in EV with a range of 50-60 miles. Of course, I'd like four seats so the whole family can pile in, but otherwise I have another car for longer trips.

  • KixStart KixStart on Feb 24, 2009

    stevelovescars makes a good point... a purpose-built PHEV, as opposed to an "upgrade" is likely to perform differently (and, we hope, better). Also, I noticed that Google's fleet of plain-Jane Priuses gets 42.8mpg while their PHEV'ed Priuses get 54.9. That's actually a significant improvement. There are lots of unknowns, of course (are the cars driven in similar or different ways, etc) but, on the face of it, it's a significant improvement for the upgrade. niky, Mostly, electricity to move a car a mile is much cheaper than gas to move a car a mile.

  • Niky Niky on Feb 24, 2009

    Cheaper. But better if it's electricity only, and not gas. Let's break the numbers down: At 54.9 mpg, you're using 4.28 liters of gasoline for every 100 kilometers ( l / 100 km is an excellent way of looking at consumption from a cost perspective). At 42.8, it's 5.49 l/100km. So, that's 4.28 l versus 5.49 l. A 1.2 liter saving per 100 kilometers... or about 1/2 gallon every 100 miles, in the same driving conditions. That's what I love about the l / 100 km. It shows you exactly how much that all means in the real world. The improvement is slight... but we haven't gotten to the best part yet... Nobody is telling us how much electricity is used to offset that 1/2 gallon. I'd prefer a purpose built EV... period. Maybe add an IC motor for emergency charging or to for emergency mobility... but an onboard charging motor doesn't have to be big enough to move the car at freeway speeds. A sad step backwards for the Prius is the inclusion of a larger 1.8 liter engine in the new model. It's simply not needed.