OK, maybe this newsflash is an obvious one to longtime green-car observers, but the folks at Pittsburgh's Carnegie Mellon found it worth publicizing that hybrids are a lot more useful to city drivers than highway hounds.

Heavy-footed driving may reduce all-electric vehicle range by as much as 40 percent.

In short, the payback for the additional acquisition cost usually associated with hybrids will take a lot longer for people who do a lot of highway driving than for those staying within the city limits and who do a lot of stopping and going. In fact, for city drivers, lifetime costs for a hybrid may be 20 percent lower than for conventional vehicles, while emissions may be cut by as much as 50 percent. Of course, big hybrid sellers Toyota and Ford helped fund the Carnegie Mellon study, along with the National Science Foundation.

Additionally, and perhaps more importantly, the report found that heavy-footed driving may reduce all-electric vehicle range by as much as 40 percent.

Unlike conventional cars, which often get fuel economy ratings that are 20 percent to 30 percent higher on the highway than in the city, hybrids see little if any fuel economy gains on the highway. For instance, the standard Toyota Prius has an EPA-rated 51 mpg city rating and a 48 mpg highway rating, while the Ford C-Max Hybrid has identical 47 mpg ratings for both city and highway driving.

Check out Carnegie Mellon's press release below. It doesn't mention diesel vehicles, but we're guessing most readers know that they're the ones that prefer to be on the highway. Figuring out the best powertrain for you really is a function of where you spend most of your driving time.
Show full PR text
Carnegie Mellon Researchers Report Hybrid Cars Are Greener for City Drivers

PITTSBURGH, June 17, 2013 /PRNewswire/ -- Will that hybrid vehicle pay for itself and help the environment? That depends on how and where you drive, Carnegie Mellon University researchers report.

Jeremy Michalek, a professor of mechanical engineering and engineering and public policy at CMU, and Orkun Karabasoglua, a mechanical engineering research assistant, analyzed the potential cost and greenhouse gas savings of hybrid and electric vehicles under different driving conditions.

"We found that for highway drivers, hybrid and plug-in vehicles cost more without much benefit to the environment," Michalek said. "But for drivers who experience a lot of idling and stop-and-go traffic, a hybrid could lower lifetime costs by 20 percent and cut greenhouse gas emissions in half."

The study, funded by the National Science Foundation, Ford and Toyota, appears in the journal Energy Policy as the EPA is rolling out new fuel economy labels starting with 2013 vehicles.

"The new labels are improved, but no single test can capture all kinds of driving," Michalek said. "Hybrid and plug-in vehicles will do the most good at the lowest cost if adopted by drivers who spend a lot of time in traffic. For these drivers, hybrids are a win-win, and the benefits may be much more than the labels suggest."

The U.S. government uses standard laboratory tests to measure vehicle fuel efficiency for federal fuel economy labels and standards.

"The fuel economy standards are still based on old lab tests that make vehicles appear to be more efficient than they really are," Michalek said. "This has always been an issue, but it is simplified with today's vehicle technologies. These tests may be underestimating the relative real-world benefits of hybrid and plug-in vehicles."

Driving conditions affect not only cost and emissions, according to Michalek. "Aggressive driving can cut vehicle range by 40 percent or more. That's a notable risk for pure electric vehicles, which already have limited range and take a long time to recharge. But with hybrid electric vehicles, which run on gasoline, and plug-in hybrid electric vehicles that use electricity for short trips and switch to gasoline for longer trips, there's no added risk of being stranded," he said.

Michalek reports that "the bottom line is: before you buy, consider how you drive."

About Carnegie Mellon University: Carnegie Mellon (www.cmu.edu) is a private, internationally ranked research university with programs in areas ranging from science, technology and business, to public policy, the humanities and the arts. More than 12,000 students in the university's seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation. A global university, Carnegie Mellon's main campus in the United States is in Pittsburgh, Pa. It has campuses in California's Silicon Valley and Qatar, and programs in Africa, Asia, Australia, Europe and Mexico. The university has exceeded its $1 billion fundraising campaign, titled "Inspire Innovation: The Campaign for Carnegie Mellon University," which aims to build its endowment, support faculty, students and innovative research, and enhance the physical campus with equipment and facility improvements. The campaign closes June 30, 2013.


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    • 1 Second Ago
  • 18 Comments
      John Fish Kurmann
      • 1 Day Ago
      Diesel-lovers mostly seem to be unaware of an inconvenient fact that undercuts their claim that diesel vehicles are the most efficient choice. Tho' diesel engines are more efficient than gasoline engines, they're also heavier, canceling out some of that efficiency gain. Most of the increase in MPG in a diesel car over a gasoline car is due to the fact that diesel is more energy-dense than gasoline - a gallon of diesel contains about 18% more energy than a gallon of gasoline. Rather than using a more energy-dense fuel, hybrids squeeze more miles out of whatever fuel (almost always gasoline) runs through the engine they're paired with. This is why hybrids engineered to maximize efficiency rather than power produce much less greenhouse gas emissions than comparable diesel vehicles. The easiest comparison is the Jetta TDi - 297 grams/mile - to the Jetta Hybrid - 200 grams/mile.
      Luc K
      • 1 Day Ago
      Prius hybrid still outperforms pretty much everything else at highway speed (unless you drive over 70-80 mph). But % difference is not quite as big in city. How many people really drive 100% highway? Consider you have to get to highway first and congestion is common for most people that commute.
        kEiThZ
        • 1 Day Ago
        @Luc K
        It's also an ugly car. I bought the only hybrid I thought was decent looking. The Jetta Hybrid.
      Neil Blanchard
      • 1 Day Ago
      Hybrids might outperform ICE-only cars, but EV's are at least 2X more efficient than any hybrid, especially in city driving. Neil
        usbseawolf2000
        • 1 Day Ago
        @Neil Blanchard
        I am averaging 132 MPGe on electric miles and 54 MPG on gas miles. Overall, 46% EV and 54% HV. Loving my PiP.
          Aaron
          • 1 Day Ago
          @usbseawolf2000
          I'm laughing at myself at how long it took me to figure out what "PiP" is: Plug-in Prius.
        usbseawolf2000
        • 1 Day Ago
        @Neil Blanchard
        There is a difference between vehicle efficiency and fuel production efficiency. To really compare gas and electric, both needs to be taken account.
          Neil Blanchard
          • 1 Day Ago
          @usbseawolf2000
          Yes, and the full energy overhead of gasoline is much higher than for electricity; so again gasoline loses. Neil
        Aaron
        • 1 Day Ago
        @Neil Blanchard
        My i-MiEV gets around 150 MPGe (calculated at the wall plug, not from the car's computer) when I'm driving normally in the city. It drops to around 110 MPGe when I'm being a little more aggressive. There are NO hybrids that come even close to either of those numbers. EVs are still far more efficient due to the fact that 90%+ of the energy is converted into motion versus 25-30% of gas being converted into motion.
        John Fish Kurmann
        • 1 Day Ago
        @Neil Blanchard
        It's true that electric motors are far more efficient than ICEs, but coal-fired power plants aren't very efficient and burning coal produces more carbon pollution than burning gasoline. That's why, in regions that are highly-dependent on coal plants for their electricity, an EV is a better choice than virtually all conventional cars from a climate perspective but worse than the highest-MPG hybrids. According to the Union of Concerned Scientists, an EV with the efficiency of a 2011-12 LEAF (34 kWh/100 miles) would have produced emissions equivalent to a 35 MPG car when charged from the 2009 grid (the most recent year for which data was available when they last updated the report in June 2012). There are lots of hybrids that are rated to achieve more than 35 MPG Combined, and at least 2 conventional cars, albeit tiny ones - the smart fortwo and the Scion iQ. You can see how a 2011-12 LEAF would've done in your region charged by the 2009 grid at http://www.ucsusa.org/assets/documents/clean_vehicles/electric-car-global-warming-emissions-exec-summary.pdf.
          John Fish Kurmann
          • 1 Day Ago
          @John Fish Kurmann
          Left something out of my comment. I meant to say that " an EV with the efficiency of a 2011-12 LEAF (34 kWh/100 miles) would have produced emissions equivalent to a 35 MPG car when charged from the 2009 grid (the most recent year for which data was available when they last updated the report in June 2012)" in the grid region that covers my home in Kansas City, Missouri.
      mark
      • 1 Day Ago
      I don't get the whole hybrids are better in town and horrible on the highway argument. I have 3 stop signs and 2 lights then all highway to work, my Camry hybrid averages about 42-47 not bad for something that's rated for 33 on the highway. When I do a lot of in town driving it seems like a lot of work to try to keep it in electric just to get 50 mpg.
      Wm
      • 1 Day Ago
      "...the payback for the additional acquisition..." I love this one. It is always assumed that Hybrids are much more expensive. In many cases they are not. I haven't looked at the prices in a little while, but when I did the Prius was $24 less than the Camry if it had the automatic and allow wheels that were standard on the Prius. Yes the Camry did of standard features that the Prius didn't have, but there were other items the Prius had that were missing on the Camry. You may say, but the Camry is a bigger car, and by some measurement that may be true. The Malibu on the other hand was almost identical in interior dimensions, yet also more in base MSRP. The Prius combined mileage was about double the Malibu, so savings started at purchase and increased with every foot driven. Not to mention the Prius depreciates at less than half the rate of the Malibu in cost less to insure. By all accounts it will be less to maintain too, even it the hybrid battery ever did need replacing. Having owned one of each, I can verify, the Prius will save money from day one and be a much nicer car to live with.
        Dave
        • 1 Day Ago
        @Wm
        "I haven't looked at the prices in a little while, but when I did the Prius was $24 less than the Camry if it had the automatic and allow wheels that were standard on the Prius." That's two different cars. The Camry starts at $22,850 while the Camry hybrid starts at $26,935.
      dewd7
      • 1 Day Ago
      I see lot of these here in Vermont. I ask, folks love them. This tends to be true for all Toyotas, of course, but they are not really big as here it is Subarus, everywhere. (Tundras/Tacomas of course). See many parked next to the family Soob, or pickup. Vermonters, the thing has to work, has to do the job, or it is out. So this admittedly unscientific analysis makes me believe the car has proved the doubters wrong. This includes me, I anticipated expensive battery issues. I still repeat those illicit glances towards first gen Insights. So that would come first. But those battery issues... Funny, here I am lusting after the one that has the problems I thought this one would have, and still forsaking it completely. Fundamentally not a Toyota guy may be the proper explanation.
      Spec
      • 1 Day Ago
      In a related study, it was determined that water is actually wet.
        EZEE
        • 1 Day Ago
        @Spec
        I was going to say, 'and the sun is hot' but you beat me to that meme. Dammit.
      JIM
      • 1 Day Ago
      Hey Danny, No this is not true, the Ford C-Max Hybrid does not have identical 47 mpg ratings for both city and highway driving. This car is a flop, a failure. CR achieved only less that 35 MPG. How many lawsuits is Ford facing because the magic number Ford advertised remains for most drivers just on paper. Even Ford itself stopped advertising its Ford C-Max Hybrid as an alternative to Toyota Prius. Sorry Ford!
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