EPA Rates Chevy Volt at 93 MPG, or 60 MPG or 35 MPG, Depending

· · 7 years ago

One day after the all-electric Nissan LEAF received its 99-mpg (equivalent) rating from the EPA, General Motors announced the Chevy Volt will carry a rating of 93 mpg while running purely on electricity, and 37 mpg in so-called “charge-sustaining” mode.

While the EPA tries to pin 60 mpg as a single composite number for the Volt’s efficiency, the amount of energy consumed will greatly depend on how you drive, the distance of common commutes, and how often it’s charged. "If you try to boil it down to a single number, it gets quite difficult," said Tony DiSalle, Chevrolet product marketing director. To make matters more detailed and confusing, the EPA also said the Volt has a 35-mile range on electricity alone and a range of 379 miles with gasoline and electricity.

Maybe the only definitive conclusion that can be drawn from the Volt’s efficiency label is that we’ve entered into an exciting new era of automotive technology, in which it will be nearly impossible to establish a one-size-fits-all number for efficiency (or for green-ness, for that matter). Plug-in hybrids, such as the Chevy Volt, that run on both gasoline and grid-supplied electricity will be particularly difficult to pin down. The phrase “your mileage may vary” has reached a new level of meaning and importance.

The quest for useful efficiency metrics was not helped by G.M.’s earlier claims that, under the most favorable conditions, the Chevy Volt will get 230 mpg; that it’s all-electric range is 40 miles; and that it will earn as much as 50 mpg after the gas engine is brought into service.

The Chevy Volt goes on sale in a few weeks. When drivers begin to report their energy consumption (and G.M. tracks usage via its communications network), a composite or average number for the “real-world” will begin emerge. Given the passions of plug-in drivers and how much G.M. has riding on the success of the Volt, even those numbers are not likely to quiet the debate about the benefits of electric-drive technologies—but one other thing is clear: plug-in electric cars like the Chevy Volt and Nissan LEAF represent a major breakthrough in fuel efficiency.

Download a high-resolution image of the Chevy Volt label.


· · 7 years ago

The EPA label says the Volt consumes 12.9 kwh/35 miles. Does this include charging losses ? If it does, what charging loss fraction is the EPA assuming ?

· Jim1961 (not verified) · 7 years ago

If you look closely at the label you will notice they break down the gasoline only mileage into city and highway. 35 city and 40 highway MPG. One of the big selling points of the Volt is that drivers can take it on a long trip. Presumably a long trip will be mostly on highways. Would it be a stretch to say that 40 MPG is what should be thought of as the real-world MPG in CS mode?

· · 7 years ago

I believe many people will consistently get 40 mpg in CS mode. But it's too early to say what the norm will be. Didn't Joel Ewanick, GM's marketing chief, get about 37 mpg on his trip from Detroit to the LA Auto Show?

@SageBrush - I'm pretty sure the EPA includes charging losses in its calculations, but I can verify.

· · 7 years ago

Driven 190 miles, with the first 35 in electric-only mode, the gasoline consumption of the Volt would be about the same as that of a 2010 Prius. Instead of paying top dollar for a Volt, one could just buy a used Prius and add a decent aftermarket plug-in conversion kit. I'm considering that option.

· Anonymous (not verified) · 7 years ago

Who drives 190 miles a day? Very few people .. most people drive less than 75 miles a day... that means most people will get over 100mpg in the VOLT .. yes that's twice as much as the Prius. And there are many everyday drivers on the road with the VOLT already.. and they are all getting over 100mpg in real world driving...Lyle author of the GM-Volt site is getting over 150 mpg in every day driving. The new sticker does not come close to the average everyday driver's experience.

· · 7 years ago

I think combined 60 MPG is wrong.
Chevy Volt can drive 13,140 miles per year on electricity alone even if it is charged overnight only: 365 * 35 miles = 13,140 miles
Average person drives 15,000 miles per year.
So real overall Chevy Volt MPG should be
13,140 / 15,000 * 93 MPG + 1,860 / 15,000 * 37 MPG = 0.876 * 93 MPG + 0.124 * 37 MPG = 81.468 + 4.588 = 86 MPG!

· · 7 years ago

Understood, most of us don't drive 190 miles a day. The point is that a regular Prius is better than a Volt for long trips. For shorter trips, it could be nearly as good if one installs an appropriately-sized plug-in conversion kit.

I'm hoping for the best for the Volt. But I'm also hoping for much better CS mileage in the next generation.

· · 7 years ago

"SageBrush - I'm pretty sure the EPA includes charging losses in its calculations, but I can verify."

Thanks Brad. My arithmetic says 20% charging losses, if we accept GM's pronouncement of 10.4 kwh/full-charge. Is that a ballpark expected number ? Can it be improved ? Or has GM cut deeper into the pack (again) without telling the consumer ?

Nosy people wanna know ;)

· Ron Gremban, CalCars Technology Lead (not verified) · 7 years ago

As others have commented, the Volt's EPA label is certainly a mixed bag. A bunch of points:

1. The 36 kWh/100mi (upon which MPGe and all else is based) definitely includes charging losses. In 2008, when the EPA reduced sticker MPG figures to more realistic values for 'ordinary' cars, it did so by increasing its fudge factor, now around 30%, added to EPA CAFE mileage (which still comes from very unrealistic tests from decades ago -- so vehicles meeting 2014 CAFE standards won't come close to getting 35.5 MPG in the real world, but that's a whole other discussion). New tests were going to be created for sticker MPG, to reflect real-world driving, temperatures, and hotel loads. I don't know if that has happened yet. If not, the same ~30% factor was probably applied to electricity usage, too, meaning that the original measurement was closer to 27.7 kWh/100mi, a respectable figure for an EV.

2. To come up with MPGe, the EPA insists on using 33.7 kWh/gal as the heat content of gasoline. This is the lower of two figures put out by the DOE, the higher being 36.4. The difference is that the higher figure includes the energy required to vaporize the water in the exhaust. I argue that that exhaust vapor energy is potentially recoverable by condensing the exhaust (as is done by high-efficiency furnaces), and should therefore be considered part of the energy content of gasoline. Once again EVs are being given less than their due.

3. For most driving regimes, Prius conversions and even Toyota's plug-in Prius are capable of far less gasoline displacement than the Volt. This is due not only to usually smaller battery capacity, but also for two reasons directly attributable to the plug-in Prius' blended mode that requires ICE power for full acceleration:

First, in order to avoid a huge pulse of pollution if ICE acceleration is required, the catalytic converter must be pre-heated and kept hot throughout the drive. For complex reasons, this almost certainly requires warming up the engine at the beginning of every trip, and running it periodically. Warming up an ICE in the controlled way that emits minimal pollution wastes at least 3 miles' worth of gasoline each time, more in cold weather, so short trips always use a lot of gasoline (reset a Prius' fuel economy gauge before a cold start and watch it get single-digit mileage for the first mile or so).

Secondly, only Plug-in Conversions' (PICC) conversions can drive purely electrically above 34 mph, and none, due to limitations built into Toyota's firmware, can provide more than a very modest 25-30 kW of electric power. While Toyota's plug-in Prius (not on sale until 2012) can drive electrically to 62 mph and 60 kW, steep hills and full highway speed still require ICE support. Maximum gasoline displacement is only 1/3 to 2/3, even if always recharged before reaching the EV range. And this figure is very driver-dependent; though I can regularly get 100+ MPG on short trips via careful driving in my PICC conversion, measured fleets of conversions have typically averaged only 60 MPG or so.

· Ron Gremban, CalCars Technology Lead (not verified) · 7 years ago

Sorry, one correction: Plug-in Supply's conversions can also drive purely electrically up to 52 mph, but once in that mode the ICE cannot run until the car is completely turned off and started again.

· · 7 years ago

I just spent about three months living in working in Los Angeles, with a one week break back home in Los Angeles. I rented a Prius for both parts of this stay and kept careful track of the mileage and the number of miles driven. I drove every day to the same place, Universal Studios, passing over the mountains on Laurel Canyon Blvd twice a day - I worked 7 days a week. In the second part of the trip I lived it the top of a mountain. The first thing I noticed was that my mileage living on the top of a high mountain, my car got about 10% worse mileage. Second, I drove fewer than 35 miles on a daily basis, not just on average but as a daily practice. So, living on top of that mountain, I would have gotten slightly worse performance per kw/H but, with the exception of two or three occasions I would never have had to use even an ounce of gasoline. Three months. No gas.

In my life in KY, on a regular basis we never drive more than 35 miles. However, we far more frequently take long car trips, to Columbus, or New York or Chicago. In those cases, the CS mode would be far more influential on the overall mileage. Even still, if we average 15,000 miles a year, only about 4,500 at most would fall into that latter category. In that case, owning a Volt, our annual average would be about 75 miles per gallon equivalent.

It is very easy to endlessly spin different formulae for determining the theoretical mileage equivalent of the Volt but it would be more effective to provide people with some easy ways of figuring out what their actual performance would be if the Volt were their only car.

· · 7 years ago

Apparently Americans drive on average 13,476 miles per year:

While yes, some of these must be long trips, I do not think that it is more than 2,000 - 4,000 miles per year. Therefore Chevy Volt average MPG must be higher than 60 MPG and much closer to 93 MPG.

· · 7 years ago

Yegor, I think you are making a complimentary point to mine, and showing that the 60 MPG figure is probably entirely bogus, or at least bogus for many. If I knew something about programming a GUI, I would come up with one so that potential car buyers could enter their annual miles drive, the extent of their daily commute, the frequency and length of their typical errands and the number and length of longer trips outside of the orbit their day to day world. It shouldn't be that hard. I did one here, in my head, drunk last night. This would allow consumers to determine which model plug-in is more appropriate for their specific situation. For instance, I do not care to own more than one car. And, given my driving habits, it is easy to see that a Volt would be a more appropriate choice than a Leaf. But, if things were only slightly different, for instance if when in LA I lived in Malibu of Thousand Oaks, my commute would be about 60 to 80 miles a day. If my partner and I lived in Cincinnati and he were to commute to Lexington to teach, then the Leaf would be the more appropriate choice, especially given that our most frequent long car trip is to Columbus, OH, which would now be in the range of the LEAF. We would still need to figure something out for the longer journeys but that is quite doable.

I write all this, not as some sort of self-obsessed public diary, but to give an example of the types of calculations that should be much more accessible to the average consumer in determining "Is This Plug-In Electric Vehicle Right for you."

· · 7 years ago

@TrasKY - Good point on the "right plug-in for you." In this new era of auto technology, trying to figure out that question is going to be the key. For your typical driving and for the money, which is better? A pure EV, a plug-in hybrid, a conventional Prius-like hybrid, or even a small 40 mpg gas car. Personally, for my family: it's all about the two car combo, one pure EV and one PHEV (when my finances will allow this transition from our current two hybrid driveway). I doubt the average American will go this same direction, but the choices are there, like never before.

I think the labels are going to become increasingly meaningless, especially the MPGe nonsense. As long as we're simplifying things to the point of total abstraction, how about this?

- Pure EV roughly equals 100 mpg
- Plug-in hybrid roughly equals 75 mpg
- Conventional hybrid roughly equals 50 mpg

And now more than ever, actual mileage (or energy consumption) will vary.

· · 7 years ago

@Ron Gremban: Thank you for the informative post. It seems quite plausible that the upcoming PICC kit for the 2010 (Gen III) Prius will be able to provide up to 60 kW, as is the case with the 2012 Plug-in Prius, without starting the engine. I do agree that the biggest issue with the current Prius for very short trips is the need to warm up the ICE. Obviously, the ideal plug-in hybrid (whether a Volt, or a Gen III Prius with a PICC kit) would allow one to drive short distances with zero gasoline.

Yes, I've played devil's advocate here. ;-) But it does seem indisputable that the Volt is currently the most gas-efficient production car for most individuals and families with only one car, assuming that they need more range than the LEAF offers, that four seats are enough, and that a Tesla Roadster is not an option.

And I'm still not sure if I really want to bother with an aftermarket plug-in kit for our Prius. Since we are a multi-car family and four seats are not enough for us, we might be better off saving the money toward a BEV for shorter drives, and mainly using the Prius for longer trips (at least 50% of our annual mileage involves trips over 100 miles).

@TrasKY: I agree that the average consumer could greatly benefit from some assistance in determining which plug-in car (or hybrid) would be optimal for their overall situation. This site is one such tool (and a good one), but more tools/"calculators" accessible to the masses would help. Perhaps a web page that asks for detailed car usage information, plus price range, and outputs a report with recommendations.

· · 7 years ago

One thing to also consider here is the fact the the volt and the prius are two completely different cars and driving experiences.

I've driven both cars and to compare anything but fuel economy would be a disservice to the volt. The prius isn't in the same league as the volt in terms of comfort, luxury and performance.

Now many people don't care about those things and only care about the most efficient way from point a to point b. Depending on how far you usually drive every day that answer could be either a volt of a prius. However if you put any kind of premium on the other factors and you can afford the extra bucks for a volt than I would recommend you test drive one before you buy anything else. It can run circles around a prius, is way more luxurious and can still deliver extraordinary economy as long as you don't drive much more than 100 miles a day.

· · 7 years ago

Sagebrush - re. charging efficiency -

10% charging loss is a reasonable ballpark to assume (all previous production EVs were in this area). I think 20% is too high. No idea if it was included in the EPA numbers or not, but I hope not. One wonders if the electricity used to pump gasoline into a gas car's tank is included in EPA efficiency numbers - of if it should be. If it were me, I'd only count tank to wheels efficiency for any type of vehicle. If we start to swim farther upstream and count "from the outlet" efficiency for EVs, then how far upstream do we swim to find gasoline efficiency? Power for the gas station? Fuel for the trucks that bring it in? Gets complicated in a hurry.

· · 7 years ago

I often read comments on various sites where people discuss the entire supply chain of electricity all the way to the coal mines and how much pollution is created and how much energy is lost along the way. They never talk about the supply chain of gasoline. I'd love to see a real side by side comparison of the entire well to wheels journey of gasoline and electricity. I can't help but think electricity would be much more efficient. Just the fact that 100% of it is produced from fuel that is acquired here in the US and not halfway across the planet would probably be enough to tip the scales.

· · 7 years ago

My electricity is made about seven feet away from the EV that it charges. ;)

Yes, this "upstream" argument is a common one. We far too often see the comparison of just tailpipe pollution from a gas car vs the full upstream pollution for an EV. Drives me nuts too!

· · 7 years ago

Darell: It doesn't seem unreasonable to count "from the outlet" efficiency for EVs, since that translates into kWh that the consumer directly pays for, much as the consumer pays X dollars per gallon of gas.

But I do love the fact that you and others charge your EVs from the sun. :-)

· · 7 years ago

Hmmm. Well... I contend that the efficiency (or pollution?) numbers for a vehicle should be independent of the "direct cost to the consumer". We should strive for an apples-to-apples comparison (which will be impossible to get anywhere near exactly right). And one consistent way to do this is to start at the "tank." If we choose to base it on what we pay... and when we pay it - we open up another big can of worms. I'm not sure why we care more about what the consumer pays for directly than what the consumer pays for indirectly. If cost to the consumer becomes part of the efficiency numbers, then we need to include ALL costs - and that's gonna be tough to figure! And even so - what does cost of energy have to do with efficiency?

· · 7 years ago

abasile, do you think you "directly pay" to protect the flow of oil across the globe? I know it's too difficult to really figure out, but we pay a lot more money for gasoline than the pump indicates. There are external costs associated with the supply of electricity also, but nothing compared to what we pay to defend and protect the supply of oil.
Wars aside, we borrow a billion dollars a day to import foreign oil, don't think we pay for that? Think again. Read this interesting article from Newsday: http://www.newsweek.com/2010/08/05/more-wars.html#

· Rob (not verified) · 7 years ago

@Abasile: You talked about modifying the Prius and making it close to being equal to the Volt. First off, that option isn't really a viable option for many of us as we don't have places that can convert our cars into a plug-in version. The average American isn't savvy enough to do the work themselves either. Second, why bother with having to buy a car and then letting it sit in a shop while it's converted with an aftermarket kit that ultimately modifies the engineered version of the car. I'd much prefer a car directly from the factory that has that option already built into it.

While I have no doubt that the plug-in version of the Prius has the potential to be better than the Volt, it's not here yet. The Volt is what we've got. And, for an average American driver, it's one of the best vehicles out there as far as fuel economy goes.

I know most of the people I know drive much less than 35 miles per day. If I had a volt, I'd probably drive it in electric mode at least 90% of the time. I've got a feeling I'd actually reach the 230 actual mpg (not MPGe) that Chevy talked about.

· · 7 years ago

@Tom and @Darrell, I used the words "directly pay" precisely because I am aware that there are many indirect costs to our energy consumption! But like it or not, the big MPG (and now kWh) numbers on EPA stickers primarily speak to what the consumer directly pays. This is (perhaps unfortunately) the language most readily understood by mainstream consumers. Some of the indirect costs are reflected in the greenhouse gasses and other pollutants figures on the sticker. It would be great to see an "energy independence" index added to that, which would clearly put EVs in a more positive light. Believe me, I'd love to quit sending oil money and our troops to Islamofascist countries!

@Rob, as for Prius modifications, there are reputable shops all around the US that will do the work for you. Typically a plug-in conversion takes no more than a day or two. People have been doing them for years now. Still, I agree that it's generally preferable to buy a production car that does what you want from day one. However, the 2012 Plug-in Prius will only go 13 miles on electricity, much less than some aftermarket conversions.

Don't get me wrong; the Volt is a very nice vehicle which will enable many to drastically reduce their oil consumption. I'm just griping a bit because I had hoped for a lower sticker price, better CS mileage, and five seats. Maybe in the next generation. Luxury is nice, but not at all important to us. Looking at the big picture, though, both the Volt and the Prius are intermediate solutions. Ultimately, I hope to be able to drive an affordable, long-range BEV and never buy gas again.

· · 7 years ago

Motortrend has one of it's "MT observed" mileage diaries - http://www.motortrend.com/features/auto_news/2010/1010_127_mpg_chevy_vol... - on line now for the Volt. As expected, the tester drives with the typical heavy foot of a driving enthusiast. Rather unexpectedly, the driver doesn't always charge the car before driving and doesn't care to keep a record of the amount of charge so that the observed mileage can't include a mileage equivalent of the EV miles driven. By adding the approximately 200 EV miles to the total miles driven and assuming about 100 miles to the gallon, it would seem that 60 MPG is the performance observed. If you read the article, this is about the worst case one could possibly come up with. The car is driven hard in mountainous terrain (Hollywood) and fast on mountain crossing freeways and there are only a couple of days of typical daily commuting use figured into the overall number. If we were to assume 5 commuting days instead of 2 and thought of the highway trip that begins the test, with the battery run down before the trip began, as a typical weekend, we would probably come up with a figure just north of 100 MPG. I think.

· · 7 years ago

I am trying to figure out what the government means by MPG equivalent. It doesn't appear to be based on emissions. It doesn't appear to be based on average electricity cost. Is there some formula that is a combination of these two things that they use? Does anyone know or should I just go and look it up?

· · 7 years ago

It's based on 33.7 kW for a gallon of gas.

By the way, it's worth revisiting this article from August:
Some observers suggest that the EPA use some kind of electric MPG proxy—a fabricated term called “miles per gallon equivalent” or “MPGe.” Duoba doesn’t like that idea for multiple reasons. After years of working on the challenge, Duoba believes that “trying to boil the information down to one number is only going to mislead people. There’s no magical way to turn electricity into gasoline.”

· · 7 years ago

I'm having this same argument on Priuschat as well - This whole energy unit issue is a problem for sure. Some contend that if you can't make 33.7 kWh by burning gasoline, then we can't compare the two this way... I content that energy is energy, and it can be expressed in BTU, Joules, Watts, TNT... whatever you want. It is a mathmatical conversion of energy units, not a physical conversion.

@ abasile - I know you know... I'm just sayin'. :-)

· · 7 years ago

I'm also not crazy about "MPGe". My beef is that MPGe does not discriminate based on where the energy comes from. 33.7 kWh generated in a renewable and/or clean manner should certainly be desired over burning a gallon of gasoline! If it meets the buyer's needs, a BEV rated at, say, 40 MPGe (perhaps an EV SUV) has the potential to be much, much better for energy independence and the environment than a Prius that gets 50 MPG. The BEV can be solar charged, while the Prius still depends on petroleum.

@Darell: Thanks. I understand. :-)

· · 7 years ago


I remember that article well and agree very much. There is so much fine print on new car stickers, it may as well be informative. It would be great if Nissan and GM and other future EV manufacturers could come up with some detailed guidelines about cost per mile and emissions per mile that were region specific. There are such huge variations in cost from region to region, not to mention from day to night, of electricity,and the sources are so varied that it is kind of impossible to come up with a one size fits all number that would even work from one state to another, much less a one size fits all number. If we start to treat people like adults, they just might actually like it.

· Car Prices (not verified) · 7 years ago

The obvious solution is that the EPA is going to have to come up with a more Honest standard that addresses the flaws in GMs publicity. A rating that measures the MPG when the Generator is actually being USED separate from the Electric motor only usage.
This seems obvious which means, of course, that GM will argue with the EPA for as long as their lawyers and publicity flacks can drag it out.
And, in the end we'll end up with something that is as close to meaningless as possible.

· clark kent (not verified) · 6 years ago

how does the volt avg. 93 mpg in easy to understand format?

· · 6 years ago

@clark kent (be real with that handle)
Easy, you put a gallon of gas in it and drive 93 miles. Of course, the net energy or environmental impact is affected by any energy that comes in from the plug as well. 93 mpg is certainly a possibility though, as is 60 mpg or 30 mpg or a lot of other xx mpgs.
I guess the upshot is that mpg is kind of a meaningless metric when it comes with PHEVs like the Volt - like the article says.

· · 6 years ago

> how does the volt avg. 93 mpg in easy to understand format?

I'll bite. How's this:

Every time the Volt travels 93 miles, the gas engine comes on enough to burn one gallon of gasoline. It might go 30 miles on day one and use no gas. Then 30 miles on day two and use no gas. So far we're at infinite miles per gallon. But on day three it travels 33 miles, and since it wasn't plugged in, it burned gas the whole way, and it ended up being one gallon. This happens every week, so the average is 93 miles for that one gallon.

· Anonymous (not verified) · 5 years ago

How big will the environmental impact be to dispose the batteries in these vehicles? I drive a diesel which is 1/2 the price of these hybrid/electric cars, gets 56 mpg highway and about 46 city. The value of my car barely depreciates, the motor can handle over 1 million miles if properly taken car of and clean diesel is used here finally and not just Europe. So where is the economical savings generated, and how many operating hours before a new battery is needed and how much do they cost to replace including disposal fees? Thanks.

· · 5 years ago

@ Anonymous -

You are comparing the cost of your car to "these hybrid/electric cars." How much do"these hybrid/electric cars" cost? If your car costs half, is it half of $25,000? Half of $50,000? The hybrid/electrics don't all cost the same, so I'm definitely confused about your cost comparison. Aren't there any other differences besides cost? Do trim levels and electronic goodies count for anything? So far, only iMiev is sold as a "stripper." Most of the others on the market are fully loaded.

You ask several questions.
1. How big will the environmental impact be to dispose of the batteries?
- The batteries are not disposed of. They are either repurposed or recycled. They are about 99% recyclable. A queston back to you: What is the environmental impact of oil changes, fuel mining, transporting and burning? Don't get confused in thinking that "clean diesel" has no emissions.

2. Where is the economical savings?
- As long as we externalize the costs of liquid fuel damage to our environment, our health and our domestic economy, the economical savings *can* be tough to realize. But in general, it is (or at least can be, and certainly is in my situation) already cheaper to operate a hybrid or EV when cradle to grave expenses are considered. We need to pay at the pump what the fuel is costing our society. Currently we don't do that.

3. How many operating hours before a new battery is needed, and how much for disposal?
- I've already mentioned that "disposal" does not happen. These are not disposable flashlight batteries. Their value, even when depleted, is significant. Operating hours are discussed in lifetimes of the cars at this point.

· · 5 years ago

Yegor, your calculation is wrong.

>> Chevy Volt can drive 13,140 miles per year on electricity alone even if it is charged overnight only: 365 * 35 miles = 13,140 miles

If we make the assumption that every single day of the year one drives the max 35 miles or more (because if we drive fewer, then that cuts down the 13,140 yearly max), then we would need gasoline only for 1860 of the 15000 total miles (to use your numbers). So the miles per gallon would be 15000 miles divided by X, where X is the number of gallons consumed for the year. We calculate X = 1860 miles / 37 mpg = 50.27 gallons.

So the mpg for the volt for that year would be 15000/50.27 = 298.39 mpg.

That is the best mpg for someone driving 15000 miles in a year.

Realistically, if you virtually never go over 35 miles in one day and always recharge properly, you can almost avoid using any gas (much less than 50.27 gallons during the year) and get over 1000 mpg. Alternatively, if you forget to recharge well every now and then and have some high mileage days, you probably can still get close to 50 mpg since that only requires you get not even half of your miles on electricity. In other words, if for every 35 electric miles you then also accumulate approximately 99.6154 gas miles, then your mpg is (calculated using harmonic average as stated below): (35+99.6154)/(99.6154*1/37 + 35*1/123456789) = 50.0000

[I used some algebra to deduce the 99.6154... as equal to 35*37/(50-37)]

In other words.. If you can avoid running on gas, you get almost unlimited mpg, and, if you use gas a fair amount (eg, 100 gas miles for every 35 battery miles), you still get 50 mpg.

>> 13,140 / 15,000 * 93 MPG + 1,860 / 15,000 * 37 MPG ....

Your calculation has the following major issue:

The (weighted) arithmetic average of the two different mpg values does not give you what you want. That is what you tried to compute.

You would need the (weighted) harmonic average: (13140+1860)/(13140* 1/99999999999 + 1860* 1/37) = 298.39.

Note I get the same result as above (when we round). Note also that I faked infinity by putting in 99999999999.

Remember, the average you want is simply (total miles in a year/ total gallons in a year).

· · 5 years ago

I forgot to clarify something.

When we do the (weighted) harmonic average on the two mpg numbers, the 2 mpg values we are using are the 37 mpg for gasoline use and infinity mpg for the electricity use. Infinity mpg = 13140 miles / 0 gallons.

Also, replace the 99999999999 mpg number I used with say 10000 mpg and you get pretty much the same thing.

· · 5 years ago

Im on the line with a big debate of Trading our MY12 LEAF on a MY13 VOLT. LEAF is a great super efficent car, absolutely love it but we are driving our 17mpg (avg) Pathfinder placing a total fuel cost around $270 per month. As wife and i alternate work schedules only one car is usualyl driven at a time, she runs the LEAF in the morning and charges when she gets home then I run the Pathfinder to and from work (70miles RT) But the debate is, if we spend a few extra bucks a month and get the VOLT, she would still be using the battery in the mornings and when I leave for work Ill average the 37-40mpg (maybe more if extra power is left on the battery).

IS it worth going down to 1 primary car and leaving the SUV for the trips where we actually need it? Seeing the Fuelly posts (not many people are using the notes sections to explain their exact driving stats) are getting a over 50MPG avg with using a good amount of fuel per 1000 miles.

I think the VOLT will cut my fuel costs in half..if not slightly more...

· · 5 years ago

Justin -

I'm having trouble figuring out why you are driving the Pathfinder. Is it because the Leaf doesn't have time to charge before you head off to work? Instead of buying new cars, you may consider putting your money and effort toward workplace charging. And... not knowing anything about your location or commute situation - do both of you need to drive a car every day? The best efficiency and financial situation comes from leaving the car at home, of course.

· · 5 years ago

@darelldd - Yes We both drive everyday. My commute is longer, hers is more around town, however I hit more traffic then she does. The Back and forth dropping the kids at school and a few errunds can be done in the SUV on days where limited driving would be done and her morning 5 mile back and forth commute (before i leave for work) could be done on the VOLT saving the fuel. I wish we could scale down to one vehicle, but its not ideal. Public transit would not help as well as it could add another hour/hour and half to my already 1hr commute. Looking at the cost benefits of the VOLT over our current LEAF, we would start saving on fuel from not driving the SUV as much but that comes at a premium cost as the curent values of the LEAFS are next to nothing. The government (even though its backed and PRO alternative fuels) will not allow any of the 4 Plug-In cars here at our compound to use the 110v outlets in the garage during the day. (main reason wife is driving the LEAF not me) Winter months i cannot make it to and from work on a charge, No L3's available yet either.

I jumped the gun on the LEAF (as did many others) no big regrets as we have saved a good bit on fuel, and as gas prices continue in the upward motion again I'm pushing back and not wanting to spend it on fuel.

DC Metro area just needs to push out the L3's and life would be simple with an EV around here......

· · 5 years ago

Got it, Justin.

My point - maybe too subtle - was to consider doing some or all the around-town running by some other means than motorized transportation when possible. I know there are many days out of the year when the weather is perfect in DC for bike-riding! Instead of buying another car, we have a tandem with large cargo bags- I get the kid to where she needs to go... get the shopping done, etc. We sometimes have two cars, sometimes one. When the second car is here, I seem to "need" it a lot more. ;)

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