We've asked in the past whether upscale and SUV hybrids -- the Accord Hybrid, the Lexus RX 400h, Ford Escape Hybrid, etc. -- make real sense, given that the increased fuel efficiency still only brings them at best to what a non-hybrid Civic might get on a bad day. But Clark Williams-Derry, at the Northwest Environment Watch's Cascadia Scorecard Weblog, employs a bit of math to demonstrate that what seems intuitively true may not be so. As it turns out, shifting from a low-mileage to a moderate-mileage vehicle has a greater positive effect than switching from a moderate-mileage to a high-mileage car.
All else being equal, switching from a 15-mpg SUV to a 30-mpg car is twice as beneficial as switching from a 30 mpg car to a gas-sipping, 60-mpg hybrid.
Here's why. Let's say you're taking a trip that's 60 miles long. The SUV burns 4 gallons of gas (60/15=4). The car burns 2 gallons -- saving 2 gallons vs. the SUV. The hybrid burns one gallon -- saving 1 gallon vs. the car. Clearly, if you have the option of upgrading an SUV to an ordinary car, or upgrading a car to a hybrid, the former is the better choice: it saves twice as much gas.
In fact, if you do the math -- and from an emissions standpoint alone -- it's just as important to switch someone from a 15-mpg car to a 30-mpg car as it is to convince someone with a 30-mpg car to stop driving altogether. For a 60 mile trip taken (or avoided) it's still 2 gallons of gas saved.
As another stark example, if a 15 miles per gallon SUV model gets 20 mpg as a hybrid -- just a 5 mpg improvement -- that reduces fuel consumption (and emissions) as much as does a switch from a 30 mpg car to a 60 mpg hybrid. (On the 60 mile trip given above, the 15 to 20 mpg improvement saves 1 gallon, same as the 30 to 60 mpg improvement.) It's counter-intuitive, to be sure -- I'm still wondering if I missed something obvious -- but the math appears to work out.
There are plenty of reasons why SUVs are dangerous -- and trading in that 15 mpg Canyonero for a 60 mpg Prius is a much greater improvement in efficiency and emissions than just moving to a 20 mpg EcoHummer. Hybridized SUVS are certainly no excuse for switching from a higher-mileage car to a lower-mileage vehicle: the math also works in reverse -- going from a 20 mpg minivan to a 15 mpg SUV is as bad as trading in the 60 mpg Prius for a 30 mpg Camry. But given the obsessive stalker love affair Americans seem to have with giant vehicles, it may well be the best course of action for car makers to focus on getting hybrid tech into the big, heavy gas-guzzlers first, where a small incremental improvement can still mean a lot.
Yep. It's not intuitive, but it's right.
Sometimes it's better to think of the number *gallons per mile* instead -- that's what you care about for any given trip.
One reason they like hybrid and suv is hybrid tech by its nature works better the bigger the car. It also works very well with high horsepower cars.
This means that not only does the math work for both doubling in mpg BUT they both wont be equal and the suv will get the bigger mpg boost!
I drive a full-sized 4x4 (Toyota Tundra), but would gladly trade it in on a hybrid. The GM I saw at a recent auto show had all sorts of features I'd love, including multiple 20A 110VAC outlets in the truck bed and cabin. I'd be able to plug in my high-draw power tools and not have to carry around a stinky, gas-powered generator.
Imagine residential landscapers using hybrid trucks -- instead of noisy, 2-stroke, gas-powered leafblowers and lawn-mowers they could use electric substitutes for many of their jobs.
Its rather common for cars to get less its also known for cars to get BETTER milage. All our cars have always gotten better milage then stated. Sometimes as in the case of our old full sized van we got FAR better then stated milage sometimes 2x stated.
Greg, the Wired piece on hybrids you link to is from last May, and it contains some serious inaccuracies (the guy cited at the beginning of the piece, for example, had a defective vehicle, if I recall correctly; his experience wasn't even close to typical). And to whatever degree the EPA estimates do overstate hybrid mileage ratings, they also do so for non-hybrids, as well (you'll get better mileage driving at 50 whether you're in a Prius or a F150, for example).
And, as wintermane elliptically suggests, actual mileage usually comes down to individual driving abilities and routes. As hybrids respond best to a driving style somewhat different from the norm, it is possible to improve results over time. I've found that I'm getting better mileage now with my 2003 Honda Civic Hybrid than I did at the outset: I get an average of 44mpg now on a tank, up from 42mpg in 2003. As I'm driving the same routes, it all comes down to learning how to drive the car better.
One reason for the hybrid gas problem is you need to do slow breaking to get the energy back hard breaking engages the breaks instead of the regenerator. Alot of people only do hard breaking.
Also if you mash down on the accellerator your gona start the gas engine sooner then warrented as apposed to slowly stepping on it and thus letting the electric motor do the starting.
Hybrids likely need a more obvious clue as to when your forcing the engine on and when your engaging the breaks or the regenerators so people can see what they are realy doing.
Person-miles-per-gallon is the best measure of marginal efficiency, at least with respect to fuel consumption. For example, a GMC Yukon that gets 15 mpg and seats 8 people gets 120 person-miles-per-gallon when full, the same as two people in a Honda Insight. Plus, in terms of congestion, parking, etc effects, it takes up less space and materials than four Insights. Then, factor in the human labor cost of four drivers versus one.
It's not just the thing but how the thing is used.
"Greg, the Wired piece on hybrids you link to is from last May..."
Facts don't disappear with age.
" ... and it contains some serious inaccuracies (the guy cited at the beginning of the piece, for example, had a defective vehicle, if I recall correctly; his experience wasn't even close to typical)."
And the same guy, after getting his vehicle fixed, saw little improvement in milage (1 or 2 MPG).
"Now Vehicle getting 36 MPG City Driving." The bad news is that while the mileage is up a mile or two (attributable to these changes)"
Did you bother to follow the link to his blog? As far as not being typical, Consumer Reports testing disagrees. They found while the typical gas engine got between 75 to 87 percent of the rated mileage, the hybrids got less than 60 percent.
"And to whatever degree the EPA estimates do overstate hybrid mileage ratings, they also do so for non-hybrids,..."
It is inherent in the EPA test to overstate a hybrid's milage by a larger degree. At the end of the article:
""The (EPA) test needs to include more fundamental engineering," says John H. Johnson, an automotive expert who co-authored a 2002 National Academy of Sciences report on fuel-efficiency standards. "They haven't been updated to encompass hybrids."
In other words, the EPA test is fundamentally flawed with regard to hybrids.