prius worth getting?

I just got a new job in Irvine and have a girlfriend in Pasadena. I moved to Anaheim so that I'm not too far from both.

Since I will be doing a lot of commuting I thought a hybrid would be a good option. I checked both the insight and prius and the prius looks like the best option, especially for traffic.

My question is, would it be worth getting a prius to save gas money?? It looks better than a insight since it doesn't run the gas engine all the time. I just don't want to waste my money buying a hybrid when I can just buy another car that burns less fuel (like a civic) for less money.

Thanks for any suggestions, Aaron

Reply to
Aaron
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If you're going to buy a new car anyway, then it's worth buying. It will cost you more than a conventional car, but you'll get a $2000 tax exemption (not a tax credit, so the tax break is $2000 multiplied by your tax bracket). Eventually, you will save in gas expenditures the difference in prices--the better mileage the other car gets, the longer it will take to make up the difference, though.

But the reason to get a Prius is not to save money; it is to cut down on emissions and to enjoy the high-tech features. :)

Reply to
Michelle Steiner

_AND_ to save money. :-)

Um, I think it's time to change sigs. :-(

Reply to
Mike Rosenberg

OK.

Reply to
Michelle Steiner

If you want to minimize your direct expenses, buy a recent used Civic. If you want get a really neat car that reduces oil imports and minimizes pollution, and you don't mind waiting for it, get the Prius.

Reply to
richard schumacher

I was thinking about buying a Prius but someone told me to lease one because new battery technology/features are coming out soon... anyone have any opinions on that?

Thanks, Aaron

Reply to
Aaron

The current Prius just started its 2nd model year, with major changes improvements in those areas. I doubt that there will be any major changes before the 2006 models.

The bottom line is that if you don't need a new car now and don't have a strong want for one now, wait until you do.

Reply to
Michelle Steiner

I am seeing more and more Prius' in the parking lots of the local malls.

If you do a lot of city driving, this rock solid reliable car should pay back within a year or two.

Reply to
obob

Prius is good for city driving, but don't sell it short! In the past few months, I have taken my 01 from Missouri to Easton, PA and home again, to Austin and back, and most recently to Atlanta, Mobile, Lake Charles, LA, and home again with flawless performance, significant velocity, and good comfort, while getting somewhere between 50 and 60 mpg. Lou

Reply to
Lou Stewart

A very good question. Because I was considering buying a Prius, I made some energy calculations to get an idea of how much gasoline is "recovered" through the "regenerative" braking.

The energy recovered from braking the car and subsequently storing it in the battery is some fraction -- less than 1 -- of the kinetic energy of the car. For purposes of calculation I assumed 100% would be recovered. The kinetic energy depends on the mass and speed of the car and is calculated from the familiar equation KE = 1/2 * m(v^2). I used 2890 lbs for the weight of the car as given in the Prius brochure (mass = 2890/32.2 = 89.75 slugs). The results at several speeds are given below:

20 mph - 50 Btu 30 mph - 112 Btu 40 mph - 199 Btu 50 mph - 311 Btu 60 mph - 448 Btu

For illustration, let's assume that if the Prius went 45 miles with no stops it would get 45 miles per gallon.

To estimate the effect of recovery by regenerative braking, assume another trip of 45 miles with stops every mile from 30 mph. That's a total of 45 stops which would recover 5,040 Btu. Gasoline has a heat of combustion of approximately 115,000 Btu per gallon, thus the 5,040 recovered Btu are equivalent to 5040/115,000 = 0.0438 gallon (5.6 ounces). We can subtract that from the gallon burned to get (1-0.0438)=0.9562 net gallon consumed to cover the 45 miles with 45 stops. The mileage with 100% regenerative recovery would be 45/0.9562 = 47 mpg, or about 4.5% better.

The recovery cannot be 100% because the hydraulic brakes come into play, there are losses in generating, transmitting and storing the recovered energy in the battery, and further losses in extracting the energy from the battery and utilizing it to power the car. I have no idea what the overall recovery factor should be, but a 50% value would reduce the mileage value to 46 mpg, which is about a 2.2% improvement over no regenerative braking.

Can't estimate how much gas is saved by stopping the engine at traffic signals. etc, because I don't know the rate of fuel consumption of the engine at idle. However, the Prius brochure lists miles per gallon at

51 hwy and 60 city, and one newsgroup poster (Jeffry Johnson) reported 44 hwy and 52 city. Both sets of data provide a crude estimate of overall mpg improvement of about 18%. Assuming the city mileage improvement is due to braking + engine stopping (because there is neither on the highway) and using 3% as the braking effect gives a 15% improvement attributable to engine stopping (any drag effects neglected).

I pondered these results for awhile and it became apparent that the advantages of the hybrid technology are not so much from regenerative braking but rather from two factors: 1) stopping the engine at vehicle stops, and 2) employing a small gasoline engine with an electric motor for power boosts when needed. Ultimately, the gas engine has to replace the energy expended in those boosts since gasoline is the sole source of energy in the vehicle.

I know this is a bit long and that it does not answer the many questions that can be raised, but it helped clarify my thinking and maybe it will help some others. Personally, I'm going to hold off on buying a hybrid for a while. Maybe a long while. Economic analysis on the cost difference of the hybrid versus the non-hybrid when compared to gasoline savings using current prices just doesn't justify purchasing the hybrid. Come to think of it, one can almost never justify purchasing any new car on an economic basis :-)

Rod

Reply to
nobody

Reply to
GAN

That's a wasted step, just changing to a different unit of mass, and one which is of no utility whatsoever in getting to the units of energy you use below, British thermal units, which are not in the subsystem of units which includes slugs. Of course, miles are also not part of the system which includes slugs, nor are hours, so you've also had to do a conversion of your speed numbers to use slugs with any meaningful results. Another wasted step. Then you've had to convert the resultant ft·lbf to Btu. Better just to use the pounds in the KE formula, and mi/h for speed, then use a conversion factor from lb mi^2/h^2 to Btu--and you can factor in the constant 1/2 factor as well. You can figure that out once and reuse it, rather than having to waste time in so many intermediate calculations.

But what is this, a drone, a driverless car? Don't you need to add in the mass of the driver? What is that listed mass for, a vehicle with an empty tank? Or one 1/4 full only? Let's just throw in a little more for driver and fuel (say you drive it from full down to a quarter tank, so use an average value of 5/8 of a tank of fuel would seem reasonable), and call the total mass 3100 pounds.

Better yet, just use the mass in kilograms and energy in joules, and energy density of gasoline in joules per liter. The calculations are simpler yet.

You also have 44 more accelerations from 0 to cruising speed, each requiring additional expenditure of energy over what would be used just in normal maintining of speed in the face of friction losses and those due to terrain, going up and down.

Gene Nygaard

Reply to
Gene Nygaard

True. I bought the Prius primarily because it saves gas, thus extending the petroleum supply, and (more importantly) it reduces emissions, thus contributing less to air pollution than a conventional car. By themselves, that wouldn't have been enough for me to buy one when I did (my former car was in great shape and was paid off, so I would have waited until I needed to replace it), but the additional gee gaws in package 9 (which is the same as package 6 in the 2005 model) tipped the scales.

Reply to
Michelle Steiner

To save gas money, no. To save on air pollution and foreign oil dependence, yes. If you want to minimize your direct expenses buy a used Honda.

Reply to
richard schumacher

Thanks for the response, Michelle. Your motivations are partly what sparked my interest in the hybrids too, along with a concern not so much for the price of fuel in the future, but its availability. In the early 1970's I was in my lower 40's with a wife and children, working for a major oil company in Texas in oil production research. I remember the oil embargo well, and I know how oil reserves are calculated. Done that. Don't put too much faith in those numbers. The input data are (is for you moderns) too uncertain. And as we know now, the numbers are sometimes deliberately falsified.

I know what you mean by the "additional gee gaws". Geez, they grabbed me too, and I came close to buying a Prius because of its cutting edge engineering. However, I'm retired and don't drive much anymore, and it won't be long before I'll be going to my Great Reward. I wouldn't get much use out of any new car.

I keep cars a long time, too. Drove a '63 volkswagon for 23 years. I drive a 10-year old Grand Caravan and my wife drives a 20-year old Toyota Cressida. They'll make a few more years.

I did the rough calculations primarily from a curiosity about the kinetic energy recovery. It's a lot smaller than I expected.

Rod

Reply to
nobody

Thanks for the response Richard. By the way, I didn't write the question above; I wrote a respone to it, but I agree with your answer. Well said! That's the story in a nutshell.

Rod

Reply to
nobody

Thanks GAN for the excellent reference. Recommended reading for anyone contemplating buying a hybrid auto.

Rod

Reply to
nobody

Weight and the slug are not different units of mass. The units of weight are force units, not mass. The slug is a mass unit as are kilograms. As to the units of energy, I can use any I prefer. If you like Joules or kwh or ft-lbs(f), use them.

No big deal. Did the numbers on a spreadsheet. Retired my slide rule decades ago.

If you plug weight (pounds force) into the KE equation I gave you're going to get the wrong answer.

Of course it's a drone. I was just making a rough estimate to satisfy my curiosity, ball park as some would say. Make any assumptions you prefer. A weight of 3100 lbs would increase the kinetic energy by 7% over my figure.

That's true indeed. Matter of fact, I did do it that way just for kicks as well as the way I posted. I was raised in the English system or something like it, so I still use it. Old habits are hard to break. I even measure lengths in feet and inches. Going to get a metric tape measure some day. Would make life simpler.

Not relevant. All I needed was the kinetic energy stored in the moving vehicle. I did tacitly assume level terrain. Should have stated that.

By the way, since this is the Prius newsgroup, do you have any comments or opinions about the car?

Rod

Reply to
nobody

I'm retired too, but about a decade younger than you apparently are. I still put quite a bit mileage on the car, though; nothing other than one supermarket is close around here.

Still, why not enjoy retirement by getting the "stuff" we like, even if our remaining years are few? My daughter and my SO are quite accepting of my plan to leave just enough in my estate to cover funeral costs.

Reply to
Michelle Steiner

If all you want to do is save money, walk/bike. You're already feeding yourself anyways. Otherwise, how about a nice used Honda Insight, Honda Civic Hybrid, or Toyota Prius? clean, good gas mileage, and since they're used they're less expensive. Or get an old diesel, convert it to 100% biodiesel/veggie oil, not so clean but no more money going for petro-fuels.

Reply to
Michelle Vadeboncoeur

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