Plug-in vehicle makers are losing out on sales dollars because the mileage ratings don't make a lot of sense. That's what one Venture Beat writer says after buying a Toyota Prius Plug-in and trying to apply the miles per gallon equivalent (MPGe) standard to real-world results. In short, it's difficult to do.

The Prius Plug-in Hybrid's 95 MPGe rating is not only difficult to quantify, but it's "artificial" and "purely imaginary" because the proportion of miles driven by electricity vs. gasoline differs from driver to driver. For instance, while a Mazda minivan costs about 21 cents a mile in fuel, the Prius Plug-in costs 10 cents a mile in gas-powered mode and about 2.5 cents a mile in pure electricity mode. For those with relatively short commutes (and therefore a higher percentage of all-electric driving), savings of as much as $100 a month are possible. Still, with electricity rates not readily available, it's impossible to measure a plug-in's powering expenses (compared to gasoline) until one measures the extra electricity used over the course of a month and adds that to gasoline-spending figures.

Even without MPGe being clear and obvious to everyone, US plug-in sales are increasing substantially. Through the end of July, Americans bought more than 55,000 plug-ins in 2014, up 51 percent from a year earlier (and those figures don't include the Tesla Model S, since that automaker doesn't break out US sales). If Venture Beat is right, then plug-in sales should be growing even faster because the public would have a clearer idea of why those cars can make financial sense.


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  • 34 Comments
      usbseawolf2000
      • 3 Months Ago
      PiP = Plug-in Prius.
      HVH20
      • 3 Months Ago
      I do 80 miles a day in my volt and drive like a jacks. 170mpg combined lifetime mileage after a few road trips.
        usbseawolf2000
        • 3 Months Ago
        @HVH20
        That's gas consumption, not fuel economy. There is a huge difference. EPA MPGe figure is fuel economy with electricity counted as one of the fuel in the equation.
      Greg
      • 3 Months Ago
      "The Prius Plug-in Hybrid's 95 MPGe rating is not only difficult to quantify, but it's 'artificial' and 'purely imaginary' because the proportion of miles driven by electricity vs. gasoline differs from driver to driver." Holy common sense Batman! Guess what? Everyone's mix of hwy/city differ, too, but somehow we manage to make sense of EPA combined mpg. Combined gas & electric is no more complicated.
      usbseawolf2000
      • 3 Months Ago
      Oh, for the EV only efficiency, I got 146 MPGe. I don't hypermile. I cross one of the busiest bridge (GWB) and running on factory recommended 35/33 PSI.
      brotherkenny4
      • 3 Months Ago
      Plug-in vehicle makers are losing out on sales dollars because the mileage ratings require that people have functioning brains, which is not that common anymore.
      BF4ALTF
      • 3 Months Ago
      The example is directed more at plug-in hybrids rather than EVs, as the title implies. Even the cost of electricity can vary. I think the MPGe is calculated based on something near $.12/KWh, what is considered the national average. But, fuel costs for gas have the same average situation with local variations. My utility offers $.06/KWh during the summer at times other than 2pm - 7pm. That would boost the MPGe to something nearing the 200 range for the PiP Prius, if charged at the lower rate and compared to the average cost of gas.
        DarylMc
        • 3 Months Ago
        @BF4ALTF
        MPGe is based on energy equivalency between gasoline and electricity. It's not based on cost equivalency, CO2 emissions or air pollution and not really useful as far as I can tell.
      Grendal
      • 3 Months Ago
      The problem isn't customers, it's the salespeople. MPGe is a tool to give you an idea of what you can expect just like MPG on a gas car. If you drive with lead footed abandon then you're going to get a lot less than the MPG. If you drive with careful efficiency then you get a lot more. It takes a knowledgeable salesperson to explain how the car works and whether it would be advantageous for your driving needs. That is why I know for certain that a lot of GM salespeople aren't doing a good job selling the Volt. It should be a no brainer sale to a whole lot of buyers. Instead the numbers are lackluster. You have to blame GM management for that. A well trained salesperson would know how to sell the car. It has incredible customer satisfaction ratings. So the fact that sales are low says that GM has not trained their salespeople how to sell the car. It's looking like European manufacturers will be beating GM at their own game because of the laws that are showing up there making an EREV something you need to buy if you don't want to get fined or even allowed into major cities. So the government is supporting electrification in ways to push the technology.
      • 3 Months Ago
      Doesn't UC Davis' EV Explorer simplify this? http://gis.its.ucdavis.edu/evexplorer/
      usbseawolf2000
      • 3 Months Ago
      We need separate efficiency of both the electric and gas propulsion with the City and Highway broken out. Many would find EV useful in lower speed frequent short City trips. While others may prefer to use the gas engine for those longer Highway drives. Having this breakdown and being able to compare them to different plugins with different battery size (hence efficiency), is what would spur more interest.
      Spec
      • 3 Months Ago
      That guy's argument is basically "I'm an idiot and I need more help!" It is not the MPGe that he is really complaining about, it is the blended average. The MPGe number does give a good indication of the savings you will get. 95 MPGe is much better than 40MPG as anyone can figure out. But the point he is making is that people will drive on electricity much more than they realize because you always drive your first X miles on electricity (where X is the AER). Yes, PHEVs can reduce gasoline usage by a HUGE amount. GM really did have a good idea with the Volt. Duh.
        Grendal
        • 3 Months Ago
        @Spec
        And the number that GM threw out there of 250 MPG seems to be a pretty accurate average. Some get more and others get less but the average does seem to be right around that number.
          Spec
          • 3 Months Ago
          @Grendal
          Well . . . 125 MPG seems more accurate after looking at Voltstats.net http://www.voltstats.net/ But yeah, even that is pretty damn great.
          Grendal
          • 3 Months Ago
          @Grendal
          I stand corrected. That is still a great number though.
      itsme38269
      • 3 Months Ago
      MPGe doesn't make a lot of sense, and even less so for plug-in hybrids. Give us two numbers - efficiency of electric drive, and efficiency of the gas engine. Really not hard.
      Joeviocoe
      • 3 Months Ago
      Seems like we've discussed this at length 5 or 6 years ago
        DarylMc
        • 3 Months Ago
        @Joeviocoe
        Probably the same outcome? I don't think MPGe is much use but if the folks in the USA think it is helpful I'm happy to leave it alone.
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