Studies Question Plug-in Hybrid Mileage

A new study conducted by Carnegie Mellon University says that plug-in hybrids with 40 miles of all-electric range are less cost-effective than hybrids with smaller battery packs.

“Forty miles might be a sweet spot for making sure a lot of people get to work without using gasoline, but you’re doing it at a cost that will never be repaid in fuel savings,” said Jeremy Michalek, an engineering professor who led the study, in an interview with Bloomberg. The study was funded by the National Science Foundation and was accepted for publication in the journal Energy Policy.

PGE Plug-in Hybrid

The Carnegie Mellon study is an attempt to test how prices and driving habits may affect consumer choices between current hybrids and future plug-in hybrids that run on a combination of gasoline and household electricity. Specific models were not named in the study. The Chevrolet Volt plug-in hybrid, scheduled for introduction in late 2010, is designed for 40 miles of all-electric driving, while Toyota’s plug-in Prius prototypes use smaller battery packs for an electric range of about seven to 10 miles.

Carnegie Mellon researchers used an electricity charging cost of $0.11 per kWh and retail gasoline price of $3.00 per gallon. The base battery cost is assumed to be $1,000 per kWh and a future low cost of $250/kWh case was also examined.

“The best choice of PHEV (plug-in hybrid) battery capacity depends critically on the distance that the vehicle will be driven between charges. Our results suggest that for urban driving conditions and frequent charges every 10 miles or less, a low-capacity PHEV sized with
an AER (all-electric range) of about 7 miles would be a robust choice for minimizing gasoline
consumption, cost, and greenhouse gas emissions. For less frequent charging, every 20-100 miles, PHEVs release fewer GHGs (greenhouse gases), but HEVs (conventional hybrids) are more cost effective. An increase in gas price, a decrease in the cost of usable battery capacity, or a carbon tax combined with low carbon electricity generation would increase PHEV cost effectiveness for a wide range of drivers.”

From Summary of Carnegie Mellon Study

The Carnegie Mellon is only the latest in a series of recent reports questioning the real-world mileage and benefits of plug-in hybrids. In its February issue, Consumer Reports road-tested a plug-in version of the Toyota Prius and concluded the cost was “more than you could ever expect to recoup in gas savings.”

“When we say we’re going to get 100 or 150 miles per gallon, then that’s setting expectations way too high. It just leads to disappointment. We need to deal in reality.”

Tom Turrentine
director of the Plug-In Hybrid Electric Vehicle Research Center

Earlier this week, the Seattle Times reported that the City of Seattle’s fleet of plug-in hybrids—designed to run for 30 miles exclusively on electricity—is averaging 51 miles per gallon. The search company Google has nine plug-in Prius hybrids used by its employees, and they are achieving an average of 54.9 mpg. These relatively low mileage numbers are partly attributed to the fact that Seattle and Google models were converted to plug-ins from conventional Priuses. Purpose-built plug-in hybrids will benefit from coordinated and optimized systems designed to minimize use of gasoline. In fact, industry observers question if miles-per-gallon is a useful measure of efficiency for vehicles that run entirely or mostly on electricity.

The Risk of Overpromising and Picking Winners

Plug-in hybrids are not expected to reach auto dealerships for another two years—while the 2010 Toyota Prius and 2010 Honda Insight, selling for about $25,000 and $20,000 respectively, will arrive in showrooms in April 2009. Toyota expects the new Prius to be rated by the EPA at 50 miles per gallon. Journalists testing the Prius and Insight have been able to achieve mileage above 60 miles per gallon. (As usual, your mileage may vary.)

The economic stimulus bill that was signed into law last week provides consumer tax credits for plug-in vehicles—offering more money to plug-in hybrids with bigger battery packs. The law does not provide consumer incentives to conventional hybrids. The stimulus package also provides $300 million for federal fleets to purchase high-mpg vehicles. In addition, automakers are vying for $25 billion in low-cost federal loans for retooling to produce high-efficiency vehicles. Government officials are now determining what kind of efficient vehicles will be purchased for fleets and what kind of technologies will be supported by the loans set aside for retooling. President Barack Obama wants to put 1 million plug-in hybrid vehicles on US roads by 2015—but some observers believe it is better for the government to set efficiency or emissions targets rather than choosing specific technologies or fuels.

“I think we all need to be more careful,” said Tom Turrentine, director of the Plug-In Hybrid Electric Vehicle Research Center, in Davis, Calif., in an interview with the Seattle Times. “When we say we’re going to get 100 or 150 miles per gallon [with a plug-in hybrid], then that’s setting expectations way too high. It just leads to disappointment. We need to deal in reality.”

  • Dick Goesinya

    Nothing but junk and smoke and mirrors. Just stick to the Regular Toyota Prius and you will be fine. The plug-ins are expensive and nobody will buy them expect the Obama loving, Latte drinking, Birkenstock save the whales customers.

  • Charles

    I think I remember people saying only “Latte drinking, Birkenstock save the whales” people would buy a Prius or any hybrid when there were only two on the market in the US. For January of this year the Prius sold about the same as the most popular Ford and GM cars (please note I said “cars”).

  • Dick Goesinya

    Just buy a 2009 Honda Fit Sport or a 2009 Honda Civic sedan and you will be money ahead then spending all this money on plug-ins. My 2005 Prius has over 100000 miles on it and going strong. Do plan to trade it in in the next couple of weeks and go back to a regular car like I stated above.

  • Samie

    Confusing article what I can gather is that the Journal of Energy Policy is peer reviewed though I’m not 100percent certain. Too many variables were left out of this article and all we have are assumptions. Therefore all I can do is speculate on whats going on here….

    Does this research consider that we are only seeing the first generation of plug-in vehicles? Would it be fair to run a study on the first generation Prius or concept and say full hybrids will be a disappointment based on the 1st Prius without considering future developments? Is there some quantitative analysis or regressions to support this study? How did they calculate electric energy to mpg’s? Does this study just consider direct costs or say hidden benefit values associated with reduction/some independence from a fuel source like petroleum or producing energy by solar, wind or other alt energy to help power the car. The biggest flaw in this study is not identifying specific models how does one replicate this study to check its consistency or add to it?

    I know there are many engineers and gear heads who visit this site so please help me with the rational behind this study, that is in a academic way..

    “The Risk of Overpromising and Picking Winners” & Tom Turrentine comments did I miss something? How long have plug-ins been on the market? whats the market share of plug-ins? Guess some just don’t see the use of innovation and cost reduction that happens on the market…. You can’t get everything you want in such a short period of time…. If that thinking prevails guess we all would have been driving the 2010 Prius ten years ago, silly indeed!

  • Dan L

    I doubt that anyone yet understands how to optimize a plugin hybrid. A few years of practical experience will make a huge difference. I would guess that unless/until battery prices come down it makes sense to tailor the battery size to an individual’s commute. So, for example, my daily commute is 12 miles round trip. A 13 mile battery would be the sweet spot. Big enough that I don’t use the ICE on an ordinary day. Small enough that I’m not paying for battery capacity I don’t use. Consider that each additional mile of electric range adds several hundred dollars to the price of the car and adds weight, lowering the overall efficiency. A car with exactly the right range makes a lot more economic sense than one with either too much or too little.

  • hybridgreg

    I agree with Samie on this one. The article was a bit short on facts. It may well be that their conclusions were correct, but as I have stated here before, basing conclusions on a study abstract (without giving the data that the conclusion is predicated on) is suspect.
    I, personally, believe that plug-in hybrids can work well. However, I do not think that using the flawed “sales pitch” formula of adding up the extra cost of plug-in hardware and dividing that by the extra fuel savings and then turning that in return on investment in years makes any sense. It works fine for salemen standing in front of a new car buyer who wants to try to sell them the more expensive SUV where the profit margins are better, but it leaves out a very large number of benefits to owning the plug-in.

    I, also, agree that trying to use a plug-in to replace battery storage capacity, instead of supplementing it, is to go in the wrong direction. Adding KW hours increases the overall efficiency of a hybrid; which is why the increased density of the lithium ion battery is being welcomed. To use the plug-in as a way of reducing the size of the gas engine and battery pack might lower production costs, but it moves the “hybrid bar” back closer to the golf cart than the long range fuel efficient goal of the next generation of automotive technology.

    I do agree with with the suggestion that the focus be on increased efficiency and not some annointed platform dictated by Washington. Too much government control to early will muck things up. Let the technology have the time to mature and then pick from the winners, instead of placing a bet on a particular system; only to be disappointed by newer developments later.

  • Gerald Shields

    Okay so even if the best you will get is 50-55 MPG, that’s still better than a Prius. Moreover, the battery technology will only get better to the point where a car can run 75% of a time on batteries.

  • David

    You’ll *never* recoup the cost of a 40-mile plug-in? Under what driving circumstances? First, do they say how much more you’re paying – how much is it that you’re trying to recoup? They haven’t even set a price on the Volt yet and CR says “you’ll never make the money back”. Then, what kind of driving do you do? A person with a 15-mile-each-way commute may NEVER have to buy gasoline EVER.

    Simple math. If the Volt sells for $40K and a Prius hybrid for $25K, there’s a $15K difference. That’s anywhere from 300-1000 gallons of gas, depending on what happens to gas prices over the life of the car. At 50mpg, that’s 15K-50K miles. Again, if you never buy gas, it’s easy to make that back. Add to that the fact that, when running on electric, you’re not putting miles of wear on things like oil, coolant and other engine parts.

    And what about insurance costs? Other maintenance?

    How about some facts, please?

  • Samie

    I’m not a engineer or claim to be, I think the research done here is not social sciences or scientific in the common way most do research but aimed at the field of engineering. Looking at the research I can see how they came up with their conclusion seeing that they question 40mpg on electric mode costs suggesting that PHEV’s should be used for urban settings and raising concerns about cost of battery technology.

    What this research fails to due which is common for some is it takes a fixed cost or technology at one point in time and make assumptions on future uses. The study recognizes environmental concerns but leaves that out in possible variables for this study??? Also again you must explain your variables that is what cars you tested to accurately make assumptions about your testing.

    hybridgreg I somewhat agree with your comment about “Too much government control to early will muck things up” In that the presidents goal of plug-in hybrids on the road is unrealistic but in terms of aiding a technology along I have to disagree with you. Lets remember that the Japanese government subsidized hybrid research and production of the Prius. This was a heavy investment on the governments behalf and took years of funding. Toyota even with aid from the Japanese government & subsidy from American taxpayers to buy the car did not make any real profits for several years despite this heavy aid. The point is without government aiding the Prius along we might not have the 2010 Prius. So in that case government maybe picking “a winning” by its heavy support. Which brings me back to this why does everybody love the Prius but at the same time bark about costs, battery technology and government policy or funding for plug-ins/long range, or EV’s when the concept of the Prius way back when was developed in the same nature????

  • wagsbags

    David, you’re an order of magnitude off. Your numbers put gas prices between $15-$50 dollars per gallon. I assume you meant $1.5-$5 which is reasonable. This means you have to save 3,000-10,000 gallons of gas or 150,000-500,000 miles assuming your charging your batteries with free electricity.

    Let’s say we get the price premium down to $5000. The volt can (supposedly) go 40 miles using 8kWh of electricity. If you get electricity at the inexpensive rate of $0.10 per kWh this is $0.80. Let’s say your comparable hybrid car gets 40mpg so takes 1 gallon of gas to go this distance. If gas skyrockets to a long term price of $3.80 you would save $3 per 40 miles driven on electricity. 40/3*5000 =~ 67,000 miles driven on electricity to recoup the cost. Only about half of driving is city driving so you’ve probably put over 100,000 miles on the car to do this so that’s the break even point. Ignoring the time value of money.

  • EnergyIndependence

    “Forty miles might be a sweet spot for making sure a lot of people get to work without using gasoline, but you’re doing it at a cost that will never be repaid in fuel savings,”

    This sentence is a key point – The costs of the adoption of plug-in hybrids is going to be repaid in more ways than just fuel savings. A key long-term objective is to move US transportation way from an oil-driven economy. This will pay all sorts of dividends down the road. And the biggest savings will be along the lines of future generations of Americans not having to pay the ultimate price for oil – their life or the life of their child on some Middle Eastern battlefield.

    Also – the government incentive programs for early adopters will help pay some of those costs as well.

    Folks really need to step back and look at the bigger picture

  • jak

    I have a 2008 Prius which I had converted to a plug-in hybrid using the Hymotion L5 battery pack. The promised range was 30 mi/ charge on battery, but that range only happens if the engine comes on often. The realistic all electric range is around 20 mi/charge. In addition, because of how the Prius gearing is set up, the car will only stay in EV mode under 33 mph (60 kph). Below 33 mph, it only goes out of EV mode when really hard acceleration is required, like climbing a hill. Above 33 mph, it goes out of EV mode at the slightest acceleration. Also, because I recharge the car from solar panels, the cost of the electricity is both carbon and dollar free. When the L5 is depleted, the car goes back into HEV mode and it is rarely possible to keep the engine off for longer periods, like a normal Prius. Between the cost of the car and the L5, the total cost was about as much as a mid-sized Lexus.

    Still, I am quite happy with the conversion. My daily commute is around 20 mi, and though most of it is on the freeway, I can usually keep the car in EV mode by driving at or under the speed limit. My only complaint is that, due to CARB regulation, the engine must come on for 5-10 min initially to heat up the catalytic converter and burn off any evaporated fuel vapors. While I understand the need for this, I think most of the reduced milage comes from this period. I have been filling up the car about once every 3 months (half tank every month and a half, around 99 mpg), but that is because I just use the car for commuting to work and around town. My wife and I have another car for longer distances (also a Prius). I remember buying and using my first 286-based PC in 1986, the experience of buying and using this car feels like the same kind of thing – a major change but also a promise of things to come.

    Regarding this study, I’m curious what their assumptions were on externalities affecting payback time. What was the assumed price trajectory for gas? Did they assume any carbon emission limits? I also think a measure of carbon generated per mile driven is probably a better measure, because if factors in the carbon intensity of the electric supply. In my case, that is zero, but it would be much more for states where coal is the primary source of electricity.

    While I agree with the basic premise that the cost of plug-in hybrids is much higher than the benefit, I believe that the technology will get cheaper, just as it did with PCs. That said, I don’t believe the process of cost reduction will make plug-in hybrids the fastest way to get radical reductions in carbon emissions from transportation. I belive that liberalizing the extremely restrictive regulations on ethanol conversions for ICEs together with massive subsidies to commercialize cellulosic ethanol production and distribution are the key. There are over 32 million cars registered in California, most of which use ICEs of one sort or another. Given the projected trajectory of the financial crisis, consumers will not have the money for an expensive plug-in hybrid, but they might be able to afford an inexpensive ethanol conversion especially if E85 is much cheaper than straight gasoline.

  • Lost Prius to wife

    “Regarding this study, I’m curious what their assumptions were on externalities affecting payback time. What was the assumed price trajectory for gas? Did they assume any carbon emission limits? I also think a measure of carbon generated per mile driven is probably a better measure, because if factors in the carbon intensity of the electric supply. In my case, that is zero, but it would be much more for states where coal is the primary source of electricity.”

    Jak, the article examined $1.50, $3.00 (their base gas price for the study), and $6.00 per gallon. As best they could, they also addressed carbon issues, including the primary source of electricity, and some of the affects of possible new technology. It appears to be a well thought out study.

  • Lost Prius to wife

    Dan L, I also want to thank you for the article.

    Samie, I was wondering about the lack of information in this article too. If you read carefully the article that Dan L cited, they chose a 2004 Toyota Prius for their “test” car over the Honda Civic and Accord hybrid and gave their reasons for doing so (I agree that it is “dry” reading and easy to miss). Their testing conditions / simulations were “U.S. Department of Energy Powertrain System Analysis Toolkit (PAST) vehicle physics similar (Argonne National Laboratory, 2008) to model and examine design tradeoffs between battery capacity and PHEV benefits.” Since they could not foresee the long term technology advances, they examined / compensated for the predicted / expected near term technology advances as best they could.

    What I find interesting is their conclusions, based on their testing, found that the lower EV run of 10 or less miles before going HEV produced the best cost efficiency and least GHG emissions. This mimics exactly what Toyota is testing for their PHEV right now. Since Toyota’s original intent for the 1997 Prius was to reduce oil usage and GHG emissions for the vehicle of the next century, their present research for the plug-in Prius may have “found” the same results as this paper did. How is that for some “food for thought”? If this study is accurate for present and near term technology, maybe the Volt is not as good an idea as most of us have been thinking. It looks like the Volt will be better than a conventional vehicle, but not necessarily surpass a conventional HEV.

    wags, the Chevy Volt is to have a 16 Kh battery, not an 8 Kh battery. And to charge a 16 Kh battery, it will take a little more than 16 Kh to recharge the battery.

  • Timothy J. Bradley

    jak – Yours was the most informative and precise post on this subject. I commend you for it. I do have a question. You mention that you use solar power to charge your battery. I had heard and believed that this process was time-consuming, unless one had a “huge array of collector capacity.”
    Would you discuss all of the aspects, including costs, associated with this solar process. Obviously, harnessing of solar power, where practical, is to be encouraged as a (not the sole, or, even necessarily the primary) integral part of reducing carbon based energy, and, of course, sooner rather than later. Again, kudos for your fine post.

  • Boom Boom

    Many of the posts criticizing this article assume that electricity is free, which is a pretty bad assumption. I think the studies conclusions look basically sound and shouldn’t really be surprising given the 20-40K cost of plug-in conversions.

    That said, I don’t think that anyone who bought a plug-in conversion was buying it mainly for the cost-return. For most it was to be an early adopter of technology and make a statement. This isn’t much different than buying a 60k BMW just because you like the luxury or performance… and there is absolutely no monetary pay back for that regardless of gas and electricity prices…

  • Carl

    Sometimes people can be so smart that they go all the way around to stupid.
    The point is that a big battery is a waste of money and resources as well as an environmental hazzard.
    What happens to an ICE when it does not run? It FAILS. The fuel goes bad. The oil goes bad. Corrosion happens.
    I would like to see a comparison of the Honda CNG fueled car to a hybrid. CNG is also more stable than gasoline and would make a good hybrid fuel. With CNG fuel less oil changes are needed and the service life of the engine is much longer.
    I can’t believe that a clean cheap and American made fuel is ignored in favor of overly complex, expensive and wastefull technology.
    Anyway GET REAL.

  • Lost Prius to wife

    Carl, although what you said about CNG burning smoother and not requiring as much tune-up time is correct, CNG will still produce CO2.

    jak’s idea of using more renewable resources is a better idea. For some of us it is just harder to do what jak is able to do. In our area, the usage of wind generators and solar panels takes a special permit. Maybe these restriction will start changing soon due to the way the world is changing around us.

  • Lost Prius to wife

    Boom Boom, how do you equate fully load Touring Prius plus taxes for $29.5K and one of the more expensive conversion kits of $15K as the same price as a $60K BMW? I do not know what you learned in high school, but I learned that $29.5K plus $15K equals $44.5K, not $60K.

    There are kits out there that are starting for $5K and going to $15K ( ,
    I do not know of any PHEV conversion kits that cost more than $20K although they may exist. If the article is accurate, the $5K conversion could return its investment in a short period of time along with less CO2.

  • Carnut

    I quickly read through the purported study (available here- with an educated eye, and I can only say that it reflects the authors’ bias against PHEVs, with ‘the numbers to prove it’.

    First the good points: The report does do a good job of framing the problem, and should have left it at that. when they start drawing conclusions, they are getting into an area they don’t know anything about, which is the current state of the art in Li-ion batteries in terms of safety, reliability, durability, cost and life. The authors base their cost/benefit recommendation on today’s costs, today’s reliability and today’s durability, while also taking a dig at safety of these systems

    Let me be more specific (to the extent possible in a public forum, based on publicly available information). What you see in the marketplace is really the zeroeth generation of automotive-grade batteries in terms of cycle life, calendar life and costs. Google up ‘Lithium Iron Phosphate safety’ and ‘Lithium titanate safety’ as well as ‘Lithium Ion cycle life and Southern California Edison’ to get a glimpse of what’s out there. If you really want to know about what’s happening with the batteries, Google up ‘UC Davis plug-in 2008 battery’ and see if you get to a download site for presentations shown at Plug-in 2008 conference during the battery workshop last July in San Jose,CA.

    the safety issue has been solved. Today’s generation zero automotive Li-ion batteries are not the ones that kept bursting only 2-3 years back (which were a fundamentally different technology popular with consumer electronics gadgets, and we all carry several of them around in laptops, cell phones and about every other gadget we own, and even their performance is now widely recognized to be safe). Same with durability. If you look at Toyota Prius circa 1997 (Gen 1 released for Japan-only), everyone, including domestic automakers, said that the cars were too expensive, batteries were too expensive, won’t perform and won’t last the life of the car. Things have turned out radically differently. In spite of what Toyota would now claim (that they knew all the answers back in 1995-1997, when they were busy making Prius market-ready), they didn’t. They have learned about Nickel-based chemistry’s suitability for hybrid application along the way and have aggressively taken advantage of the benefits. Latest indication from *actual* battery testing and by connecting the dots from what GM is doing, is that Lithium-ion technology will go *beyond* the life of the vehicle, which is 10 years, 150,000 miles. At some point in the life of any vehicle, components – even engine – fails and needs to be replaced. US car park’s average life expectancy is about 15 years. The average car performance and fuel consumption degrades over its life (an engine that is just ‘broken in’ performs way better than the same engine at say, 100,000 or 150,000 miles – same with batteries).

    Specifically in terms of battery costs, technologies in the pipeline today will get the costs down to levels that are 60-70% of the levels today, and asymptotically you could be seeing them coming down to 40-50% of where are today – all in (i.e., cells plus all that hardware surrounding it).

    GM is doing plug-in Hybrids for precisely the same reasons (and under the same competitive space) as why Toyota did Prius – to gain a technological upper-hand and get ahead of the competition by one generation of technology, product, manufacturing and market learning.

    So, the conclusion is that the authors have been either blissfully or willfully ignorant of all of these facts in public domain to paint an unnecessarily bleak pictures of comparing a 3rd or 4th generation Prius with plug-in technology that is still not in consumers’ hands, has not proven itself and will have its own path (and challenges) to widespread adoption.

    I could write another 36 page study as to the methods the authors have used, each assumptions of which are suspect and without any technical (experiantial) basis, but that’s not needed.

    Bottom line is that the purpose of research should be to provide the tools and insights to provide an unbiased assessment of the technology, which this study miserably fails to do.

  • Pablo

    “Carnegie Mellon researchers used an electricity charging cost of $0.11 per kWh and retail gasoline price of $3.00 per gallon.”

    $3.00 per gallon could work as estimated average price for 2008.
    It it too low as estimated average price over the entire life of the vehicle. The average life of a vehicle is 16.2 years! They should predict the price at least 10 years from now and use that price.

    In the Summer of 2008 the price of gasoline in Europe was $7 to$10 per Gallon, I was there to see it personally.

    Even now the gasoline will be ~$4, instead of $2, if the hidden subsidies are taken away. In addition we need to price in the air pollution, global warming and strategic dependence.

  • Carl

    All cars generate CO2, it just comes from a different source.
    Electric cars are powered by coal, nuclear,hydro, wind ,solar, probably in that order. The only thing cleaner than CNG is hydrogen and that generates CO2 in the making of it.
    Why choose the technology that isn’t here?

  • Doug Korthof

    Carnegie-Mellon: complete and utter bullshit. These bogus “studies” are twisted to discredit Electric cars, probably funded by the oil companies.

    You have to look at the hidden cost of gas, which is about $15/gallon (think about the trillions spent defending Chevron’s mideast and other oil supply lines!).

    Moreover, people who start to drive Electric don’t CARE about the cost, they just want to continue. It’s a big treat and lots of fun to drive oil-free.

    So why not let us??

    Why not allow some people to have an EV or plug-in??

    Just because it’s not for everyone doesn’t mean it should be kept from everyone. Actually, I think the real fear of the oil companies is that it WILL be for everyone!!

    That’s what they really fear, and that’s why they pay corrupt academics for B.S. Studies like this.

  • Doug Korthof

    We get our electric from rooftop solar panels! It only takes 250 kWh, about a third of the average home’s usage, to drive 1000 miles per month!

    And you can charge slowly at night, helping the grid, while your solar panels help the grid meet daytime peak. Actually, lowering emissions for each mile you drive! Because big generators don’t have to be shut down to “warm start”.

    Best of all, the money we save NOT buying gasoline more than pays for the solar rooftop system!

  • Doug Korthof

    View our solar panels, which powers TWO Toyota RAV4-EV all-electric oil-free plug-in cars!!

  • Flex23

    Carl Or is it Exon Carl/CNG?
    “CNG is also more stable than gasoline and would make a good hybrid fuel” Explain where CNG comes from & the supply in the U.S. CO2 and extraction of hydrogen from oil reserves hmm something doesn’t add up. Hidden cost of gasoline –> hidden cost of CNG
    Not producing your own energy sounds really exciting to me,
    Zombies for CNG

    Read Doug Korthof & Pablo’s comments.

  • Wil

    Actually, I routinely get 55-60 mpg from my 2007 Prius — and that is with about 85% freeway driving. Just drive carefully and without the jackrabbit starts and excessive speeds.

    Aren’t plug-in hybrids touted for far more than **that**?


    I have not yet read the Carnegie Mellon study itself. However, it IS true that Prius conversions suffer from limitations that require simple modifications to driving style — usually not applied by fleet drivers — to maximize electric drive, displace a lot of gasoline consumption, and thereby get 100+ mpg (plus electricity) until the battery is depleted. After doing the first conversion in 2004 to pressure the auto manufacturers into building PHEVs by showing that the technology already exists in a mass-produced car, we at CalCars initiated the “100+ mpg” slogan to publicize what we accomplished that most commuters should also be able to achieve once purpose-built PHEV passenger cars become available.

    In addition to using gasoline efficiently, the important thing a PHEV can do that an ordinary hybrid cannot is use electricity as a fuel to displace gasoline. This is not as important today as it will be soon, as, to avoid climate and energy security calamity, we must move toward an 80% reduction in greenhouse gas emissions from 1990 levels by 2050, which ALL NEW vehicles will therefore have to reach by 2035. We can’t grow enough biofuels for hybrids to do this, but with vehicles mostly powered by renewable electricity we can! And we must begin down the curve of volume production and lowered costs NOW to have a prayer of getting there.

    A well-designed PHEV of any size or vehicle type can displace 35-50 gallons of gasoline per kilowatt-hour of battery capacity per year. This assumes that its battery is fully depleted once a day. Therefore, tailoring a PHEV’s All Electric Range (AER) to each driver’s daily routine is economically important, as the best cost-benefit is attained when the battery is fully depleted, or nearly so, between each charge.

    However, most of an auto’s criteria emissions occur, and around 2 miles’ worth of gasoline is wasted, with each cold start — so an AER tailored to each consumer (e.g. via battery size options) to be just long enough to make routine daily driving all electric would likely provide the best overall economic optimization. Of course, once electric propulsion is common, battery prices will be on a downward curve and the sweet spot will lean increasingly toward electricity.

    Another point is that it may be best to focus electrification efforts on the larger vehicles that eat up the most gas — SUVs and trucks of all sizes — as well as work to entice people toward buying and driving only as large a vehicle as they really need.

  • hybridgreg

    Having recieved CalCars publications since 2007, I know the great work you guys have done to promote this technology. In fact, I believe that PHEVs might be the key to convincing the public to have confidence in all-electric vehicles. Converting hybrids that are already on the road to PHEVs seems like a difficult uphill battle in California. With the Air Resources Board view that installers must first pay for extensive emission modification testing, I wonder if the ARB is being influenced by the OEMs or some other group trying to block the advance of the technology. What do you think, Ron? Otherwise, why would they place such a great economic burden on these installers at a time when PHEV technology is beginning to to catch fire?

  • Carl

    This is interesting.
    Without regard to cost , efficiency or environmental impact,some people just want to drive electric cars! Fine, just understand what you are doing.
    Every time energy is stored or converted to another form, there is a loss.
    Start with natural gas, burn it in a power plant, transmit the power over wires (loss) then run it through a transformer/controller/charger (loss) then convert electrical energy to chemical energy in the battery (loss) then store that energy when the car is not running (loss) then convert chemical energy back to electrical energy (loss) then convert to mechanical energy in the cars motor (loss). Talk about hidden costs.
    How many Prius drivers come back from a trip and find the battery dead? Then tow the car to a dealer. Great mileage!

    You say solar is clean? Do you know how much chemical waste is created to make those panels?
    I am not opposed to electric cars, just to people who put on blinders, ignoring the costs. The best answers involve a mix of technologys to achieve efficient use of resources.

  • jak

    We had the solar panels installed in 2004, a 2.5 kw array sized to cover 75% of our electricity needs yearly. With rebate from the state of California and tax deduction, it came out to about $18,000. I think it would be around $12,000 today (and today you can also lease panels, making the downpayment nothing). By eliminating outmoded appliances (primarily two pool pumps and a refrigerator) and switching to CFLs, we now have about 1000-2000 kwh per year of extra, depending on the year, that we typically give back to PG&E, because California’s NetMetering law doesn’t allow you to be reimbursed (they since have introduced another tariff for that, but the NetMetering tariff is still more attractive for normal homeowners). Frankly speaking, having the solar array installed was one of the easiest home remodelling efforts I’ve ever undertaken, though we did have a subsequent problem with roof leakage due to inadequate cauking that was easily fixed.

    The car takes 5 kwh per charge so if I charge it every work day, it would be 1300 kwh per year for communting. As a practical matter, I don’t commute by car every day, in fact, in summer I rarely use the car because it is easy to commute by bike and the exercise is great. So the car charging essentially comes “for free” from the extra we would normally give back to PG&E. The original payback time for the solar array was something like 15 years, it would be interesting to calculate how that changes when I can displace 20 mi of gasoline per commute. I calculated that the plug-in displaces something like 66% of the CO2 the car would normally generate, it would be great to get that up to 80% with something like an ethanol conversion, but that looks to be tough since nobody markets a CARB-approved ethanol kit for the Prius.

    Regarding practicality of charging, I’ve strung an extension cord from a 110v/15amp socket to the front of the garage (I originally wanted a plug in the floor that would come up on a spring, but the cost of installing that was too big for one car). The cord is on a mechanical timer that goes on between 11 PM and 5 AM when power is cheapest. By the NetMetering tariff, PG&E pays about 3x for power in summer during 11 AM and 6 PM because that’s when they have air conditioning peak load, so I don’t want to charge it then. The car takes about 5 hr to fully charge, but it is about 2/3 to 3/4 charged within a couple of hours. I wanted a 220v charger too for faster charging but Hymotion only supplies the conversion with a 110v charger because – kind of like the original Toyota Prius commericals about not having to plug it in :-) – they were concerned about consumer acceptance. What would help more than anything else is to have the opportunity to charge the car when it is sitting around parked somewhere, like in the company parking lot or downtown in a garage, though of course the power in that case wouldn’t be from solar panels.

    Hope that helps.


  • Daniel Sherwood

    The CARB requirement to run the engine for a few minutes on startup is indeed what is causing the mileage on these plug-in hybrids to be so disappointing.

    Our company 3Prong Power Inc. has a conversion that allows you to turn the motor off completely and drive around town up to 50mph as an electric vehicle only until you run out of battery power. The engine never comes on in this mode. Right now the mileage I get on my commute to work (admittedly less than 10 miles from my house) is infinity miles per gallon.

  • steverino

    What’s the payback for a car that has a built-in to safety net for the next gas embargo? A plug-in hybrid is like an insurance policy against disruptions in oil supply. Ass you need to is look at what Russai did to Europe this winter when they embargoed natural gas during peak demand in winter. What is the payback for cars that lessen our dependence on oil imports? What is the payback for cars that don’t send dollars to mid-east Shiekdoms who in turn fund religious extremists? The study apparently gives these considerations zero value.

  • Rob Smith

    Regarding Jak’s question above about the payback period of solar used for cars vs. regular household use. The answer is it pays off a lot faster. For example, here are the number using the current incentives here in AZ:

    Miles per year: 12,045 (33 miles every day)
    Assumed Efficiency: 250 AC Wh/mi
    Annual Consumption: 3,011 AC kWh
    Required DC System Rating: 1.88kW (@1600 kWh/yr/kW DC)
    Assumed System lifetime: 20 years

    Est Upfront Cost: $13,174 (assumed $7/W installed)
    Util Rebate: -$5,646
    AZ Tax Rebate: -$1,000
    Fed Tax Rebate: -$3,952
    System Net Cost: $2,576

    Low Fuel Offset Estimate: 5,236 gallons (vs. 46mpg)
    High Fuel Offset Estimate: 10,950 gallons (vs. 22mpg)
    Est 20 Year Av Gasoline Price: $2.73 ($2/gal, increasing at 3% per year)
    Est Value of Offset Fuel: $14,294 – $29,893
    Break Even Point: <5 years - <2.5 years
    Annualized ROI: ~23% – ~53%

    This analysis is for the solar alone. It does not include the cost of the conversion, or premium for a factory PHEV.