Posted on 12/13/2006 9:59:41 AM PST by Entrepreneur
I ran across a report by the Idaho National Laboratory where they compared fuel efficiency of hybrid vehicles with and without air conditioning. You can find the report below. Page 17 shows the comparisons.
http://avt.inl.gov/pdf/hev/sae_gov_ind_may_2005_hevs.pdf
Given that the acclaimed fuel efficiency of hybrids is much less with the air on, I wondered how they compared with standard vehicles. Using Edmunds.com, I made a few direct comparisons. This is interesting stuff…
2003 CIVIC...
2003 Civic Hybrid
Air Off: 47 MPG
Air On: 36 MPG
2003 Civic LS Auto 4 Cyl.
City: 29 MPG
Hwy: 38 MPG
Avg: 33.5 MPG
2005 ACCORD...
2005 Accord Hybrid
Air Off: 29 MPG
Air On: 24 MPG
2005 Accord LX Auto 4 Cyl.
City: 26 MPG
Hwy: 34 MPG
Avg: 30 MPG
2005 Accord LX Auto 6 Cyl.
City: 21 MPG
Hwy: 30 MPG
Avg: 25.5 MPG
2005 SILVARADO...
2005 Silvarado 2WD Hybrid
Air Off: 16 MPG
Air On: 19 MPG
2005 Silvarado 2WD Hybrid
City: 16 MPG
Hwy: 19 MPG
Avg: 17.5 MPG
2005 ESCAPE...
2005 Escape 2WD Hybrid
Air Off: 25 MPG
Air On: 32 MPG
2005 Escape 2WD 3.0L
City: 20 MPG
Hwy: 25 MPG
Avg: 22.5 MPG
COMPARISON...
I compared the hybrid fuel savings with air on to the conventional vehicle’s city/highway average. The Civic and Escape hybrids each got a whopping 2.5 MPG better than the conventional vehicles. The Accord and Silvarado hybrids performed worse!
Civic: Hybrid +2.5 MPG
Accord 4Cyl: Hybrid -6 MPG
Accord 6 Cyl: Hybrid -1.5 MPG
Silvarado: Hybrid -1.5 MPG
Escape: Hybrid +2.5 MPG
In some parts of the country, people may not need air conditioning. Where the air is kept on most of the year, the hybrids aren’t such a good deal. In fact, they may get worse fuel efficiency. And we haven’t even discussed the energy cost to recycle the batteries every eight years.
Am I wrong, or do hybrid vehicles (today, at least) appear to be another feel good/do nothing hoax?
My old Chevy Sprint got better mileage than that, without the expensive electric car crap.
well, hydrogen vehicles pollute more (due to great energy needed to produce the hydrogen), so your findings are not suprising:
http://www.freerepublic.com/focus/news/1284737/posts?page=1
Gosh, it'll only take 743 years to recover the initial opportunity cost lost in purchasing a hybrid.
Where are the #s for conventional vehicles blasting the a/c? Comparing apples to apples is a good plan.
(also, your figures seem backwards, unless hybrids get more mpg by turning a/c on...)
I'm a mechanical engineer by training, so I try to keep up on the car technology. I'm rebuilding a 67 Camaro with an eye to efficiency. Most new technologies have a very large indirect cost that is rarely computed (either in greater breakdown frequency, materials costs, or loss of capability).
I think you have hit on a great point about the air conditioning. Hybrids depend on running a high effiency constant process with some sort of secondary surge demand. Problem is, air conditioning requires enough horsepower to start to push the system over into the inefficient surge demand operating band.
I've been looking at a way to offload accessory power demand from the engine, but there are a whole lot of variables.
Also helps keep the rust away, I run it all winter with the heat on.
Btw~ what a stick in the face, as the watermelons see me luxuriate by them in my antique living rooms on wheels in showroom condition.
I have a 2005 4 cyl 5-speed manual Accord and it consistently gets 33-34 MPG on a tank of gas ~13 gallons. Most of it is expressway miles (90%), but the overall number is impressive compared to my prior vehicle. Running the A/C doesn't seem to affect it that I can see easily.
I think the downside of a hybrid is that I've heard their strong suit is in city, stop-go-driving; they don't seem to be very efficient at sustained highway speeds....
At highway speeds, conventional gasoline vehicles get better mileage with the windows up and A/C on than with the windows down and A/C off. Wind drag.
Well, I can speak to this subject being that I own a 2006 Escape Hybrid. I also owned a 2003 V6 Escape before that. Both use energy when the A/C is on although the loss is greater with the hybrid. When the a/c is on with the hybrid the gasoline engine runs continuously in the "full-on" mode. So that would account for the significant decrease in mileage. I'm getting about 29-30 mpg with the hybrid and the V6 was about 20-21 mpg overall. The drop in mileage during the summer is around 5 mpg. Which just goes to prove that energy use goes up when more energy demands are made on the vehicle.
I regard the battery issue as a unimportant. It is warranteed for 8 years and 100,000 miles.
I got a '95 Jetta that gets 33mpg. Or, 30mpg with the A/C on. I paid $1200 for it.
Good for you.
I have an '07 Toyota Camry Hybrid. I'm getting 38 mpg. The air condition runs on the electic motor, not gas. It is a wonderful vehicle.
What do you do w/ it then?? Toss it away - or purchase new batteries and recycle the old? The costs to replace should be figured in somehow.
It does, but that is counter acted by loving the smell of your own farts so much you fat more
Interesting numbers.
My 2000 Subaru GT LTD with 165HP 4 cylinder get 21mpg city and 27mpg highway. It seems most hybrids are not working so great.
Heck, my 95 Saturn SL2 with the DOHC 4 valve per cylinder engine got better mileage than this!
They should be recycled. They are nothing more than a number of smaller batteries tied together just like the battery packs in portable drills, etc. They could also be repaired if necessary, be replacing the bad cells.
I've also seen these on ebay (out of scrapped vehicles) for little or nothing. They appear to be easy to get to being that they are just below the carpeting in the cargo area. The spare was moved below so there is no difference in capacity. Looks to me like a simple drop in procedure. I doubt if I will be doing that as I seldom keep my vehicles more than 3 or 4 years anyway.
Background / Current Tests and Methods
The city and highway MPG estimates have been provided to consumers since the 1970s as a tool to help shoppers compare the fuel economy of different vehicles. Currently, EPA relies on data from two laboratory tests to determine the city and highway fuel economy estimates. The test methods for calculating these estimates were last revised in 1984, when the fuel economy derived from the two tests were adjusted downward—10 percent for city and 22 percent for highway—to more accurately reflect driving styles and conditions.
The city and highway tests are currently performed under mild climate conditions (75 degrees F) and use acceleration rates and driving speeds that EPA believes are generally lower than those experienced by drivers in the real world. Neither test is run with the use of accessories, such as air conditioning. The highway test has a top speed of 60 miles per hour, and an average speed of only 48 miles per hour.
Since the mid-1990s, EPA's emission certification compliance regulations have required the use of three additional tests which capture a much broader range of real-world driving conditions; specifically: high-speed, fast-acceleration driving and the use of air conditioning and colder temperature operation (20 degrees F). Not only do these conditions impact the amount of air pollutants a vehicle emits, they also have a significant impact on a vehicle’s fuel economy. However, they are not currently required to be used to measure fuel economy.
Top of page
Wish I could find it now, but can't. Remember reading a report that determined you would need to drive 50,000 miles a year for 5 years to recoup the intial increased cost of a hybrid vs. 15,000 miles a year in regular car.
Myth Busters did an episode on this. Can't remember the outcome. Anybody?
My 1996 Lincoln Town Car gets about 20 mpg around town, and 23 mpg on the road. That's with climate control on.
I find myself unable to get excited about the new hybrid technologies, particularly when I consider the comfort bestowed upon me by the Lincoln.
I have a 2005 Huyandai Elantra. My commute is about 21 miles. Half in bumper to bumper at a minimum, usually closer to 3/4. The remaining is at highway speed, about 65 to 70 MPH. I avg 30 MPG.
They tested at low speeds -- the windows won.
However, drag goes up as the square of the speed, and the fuel consumption/time goes up as the cube of the speed -- while the A/C load is constant (given constant weather). At higher speeds, the A/C wins. The more aerodynamic your vehicle, the more you would notice the additional drag.
Those are some really wierd numbers. All of the American hybrids are listed as having higher mileage with the air on than off. And how is Honda selling a single Accord hybrid if it gets lower mileage than the 6 cylinder auto?
Aside from that, you should be looking at relative percents when judging the impact of the A/C. For example, the Accord Hybrid goes from 29 to 24 MPG when you turn the air on. The percent impact is (24 - 29) / 29 * 100% = -17.2%. Running the same calculation for the other two Accords gives -23.5% for the four cyl. and -30% for the six. So the hybrid actually suffers less impact.
I want to see them take into account the electric strip heat. LOL.
The Honda Hybrids are serial hybrids, and use the motor to augment their engine. The A/C runs off the engine, and they save gas by not burning off gas for power they don't need.
As you use more power, the gas mileage will approach normal cars at their own peak power, because in the end you are just burning gas in an engine no matter what car you have.
The Toyota Prius/Camry (new model Prius, not original) use an electric compressor for the air conditioning, so they don't have to run the gas engine when you turn the A/C on. That means they do better with the A/C than cars like the Honda Civic.
The Ford Escape is designed around the Toyota "parallel hybrid" concept, but I don't know for sure if they use the electric A/C. Some normal cars are going toward electric power for the A/C and power steering, because it is more efficient since you don't have to run the engine.
One thing that this shows is that hybrids are not magic, they simply waste less of the energy. Your normal car is wasting so much power that you can turn on the A/C and hardly notice a difference, because you are just using some of the wasted power to run your A/C.
The Mythbusters did a fascinating test to see if you'd do better in a Pickup Truck if you put the tailgate down to "decrease drag". Seemed like a good idea, but they actually got a LOWER mileage with the gate down.
They did a quick wind-tunnel test, and found that the design of the truck bed was such that it set up a vortex (with the tailgate up), which effectively put a cone over the bed, allowing air to pass OVER the entire bed/tailgate.
With the tailgate down, the effect was lost and drag increased.
Dont need the AC here in Alaska, I would be very interested in the same kind of test at 30 below with the heater running on full.
"Myth Busters did an episode on this. Can't remember the outcome. Anybody?"
IIRC their test showed that it was a myth that running the A/C and keeping the windows up was more efficient due to improved aerodynamics of modern cars.
But their test was crap. They tested a big, bulky Suburban or Tahoe SUV, which has a really lousy coefficient of drag. If they had tested a smaller, more streamlined vehicle they might have gotten a completely different result.
Based on what I've seen with hybrids and my daily commute (100+ highway) I don't see where they can save me anything...
I see pickups all day long up and down the highway with the tailgates down and they don't even know it's not helping anything, even hurting in some cases....
TANSTAAFL....the electric motor takes current, current is produced by the alternator to charge the battery and provide excess, when the alternator has to work harder, it provides torque resistance to the drive belt, ergo, more HP from the engine....same thing with lights, etc....
I think it's because of the better city mileage.....because it sure isn't better on straight high speed highway...
I like the idea of hybrid vehicles, but in my opinion it has been approached from the wrong engineering direction.
A more economically successful "hybrid" would be a straight out electric car that is occasionally used for longer trips.
Considering that most trips are back and forth to work, to school, or to the stores, an electric vehicle would suffice for most purposes. But rather than have two vehicles, having a generator pack for the electric would allow it to be used for longer trips when needed.
And in order to maximize the efficiency of the "generator pack," when it is not needed for the car, it should be connected to the house, preserving its energy requirements.
Two birds with one stone, over and over again. An electric vehicle to commute back and forth to work. An emergency home generator that can be used in the car for vacation trips.
Glossing over the problems with batteries for the moment, consider how the electric car can be made most optimal. It could be equipped with a shell of solar cells which would charge the battery and shade the vehicle while its driver is at work.
More attention could be paid to the suspension and drive train for energy recovery options also.
Concentrating on the car alone, to the exclusion of current lifestyles is what gets us inefficient hybrids.
The use of electric power in a Prius is indirectly tied to the engine, not directly. There is no "alternator". There are two electric motors, both of which can run as either motors or generators as necessary.
The computers determine when the gas engine is needed to charge the batteries or to provide direct electric power (through the use of one motor as a generator).
When a gas engine is operating, there are narrow bands at which they are the most efficient. The Prius attempts to run the gas engine in that narrow band, which means a narrow range of output power values. When that power is greater than what is needed currently for the operation of the vehicle, the excess is dumped into a large battery. There is a loss dumping power to the battery, but that loss is less than the loss of running the engine at a less-optimal power level -- if not, the Prius computers won't bother.
The Prius also uses the motor/generators for braking, so it can charge the batteries with what would be wasted power.
If the type of driving you do would normally cause you to operate the gas engine in a sub-optimal power range, the Prius will improve your mileage, sometimes dramatically.
If you tend to already drive a car in the optimal range, a Prius wouldn't do as much for you, although the use of the battery allows the Prius to operate in the optimal range almost always, UNLESS....
If you tend to maximise the use of power from your car (floor it all the time), and then heavily brake, you won't get really good mileage in a Prius relative to a non-hybrid, because you aren't really letting the Prius steal spare power for use later.
On an almost unrelated note, the Prius implements "engine creep", by putting a small amount of power into the electric motor when the car is going less than 7 MPH and you don't have the brakes on enough. A lot of people don't know this. If you tend to ride your brakes LIGHTLY in those modes of operation, or if you only lightly use your brake when stopped, the Prius will actually feed power to the motor to try to move when you won't let it, and this can significantly reduce your mileage.
It's probably the number one reason people who do a lot of stop-and-go driving DON'T get the great gains they would expect.
Otherwise, stop-and-go is where the Prius shines, mostly because it simply doesn't run the gas engine when it isn't needed, and an engine not running uses a LOT less gas than even a well-tuned engine that is idling, even at stop.
This is not a "hybrid" unique feature, with nothing more than a better starter motor, you can implement engine stop for almost any car. It just comes a lot easier for a hybrid.
I'll take your word for it, but it's hard to believe there is such a thing as a free lunch (even under wierd circumstances) with a Prius or similarly equipped vehicle. I still don't think I'd buy it because I don't believe the maintenance and durability costs would be good...that is, unless the government ecofreaks would give me a full price tax credit! Then, I'd do it.
It's kind of what the Prius developers went through. Start with an Electric car. But you want to go further, so you add a generator, which you want to run at a constant speed in it's optimal power efficiency torque range (please forgive the inappropriate use of the language).
Nobody wants to tow a generator behind the car, so we build it in. But now that we have the gas engine built in, turns out that we could ALWAYS run it, just at it's optimal speed/torque/power point. And if we do that, we will always have a 10 percent loss charging and discharging the battery, or even generating power to use in the electric motor, so instead we use a direct gear connection so that, when the gas engine is running, we can feed it's power directly to the wheels, which is more efficient.
And thus you have the Hybrid Prius power train. By connecting the gas engine, you don't need as big of an electric motor. And you don't need as many batteries, which lowers cost and weight which saves gas as well.
It is true though that they didn't optimize everything. Prius experimenters have found that having twice the battery storage capability can significantly improve your gas mileage, if you drive "appropriately". I knew one guy who could do better than 80 mpg with his Prius with an extra battery, over LONG distances, once almost 900 miles.
DOn't think of it as a free lunch. Think of it as a free dinner.
Meaning, you go out to lunch, you buy a big meal, you can't eat it all. A normal car would be like throwing the food out. The Prius is like getting a doggie bag, and eating the leftovers for dinner.
I would be looking for a cross between a fully solar car and a hybrid. The vehicle could be optimized for individual usage.
You have to commute twenty miles to work? You'll want something that provides at least fifty miles range. Add extra batteries to extend the range.
Use solar cells on your house to charge an extra battery module, which you can load on to your vehicle by backing into the garage, and drawing it up a ramp under your trunk like a rollback truck. As it seats and secures itself, the connections are automatically made. You could either have battery sets side-by-side, or have one battery and one gen-pak.
Motor-generators in each wheel, with maybe a "fifth wheel" comprising an energy storage flywheel for quick acceleration or hard braking. Energy would be coupled into and out of the flywheel without the speed limitations of charging and discharging a battery. Once the vehicle is parked, the flywheel could be "spun down," storing its energy in the battery system.
While warming up the car before leaving your house, you could "spin up" the flywheel using house power.
With energy collected from every bump in the road, and every tap of the brakes, a light vehicle could have an appreciable range, and that range could easily be extended by coupling more capacity in.
The secondary advantage of a house/car integrated system is the energy security within the house. If power fails, the emergency circuits could automatically draw from those componets of the automotive system that were online. If the car is at home, all systems should be fully charged at the time the power goes off, and they should stage their recharging when power is restored to minimize surge.
I live about 20 minutes from Cambridge. What we need is a car that runs on earth-friendly and environmentally sustainable whale oil. I'd buy one.
The day they try to take my A/C away is the day I will truly begin to fear for their survival!
"But they drove with pride... in a hybrid."
-PJ
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