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Allow the driver to enter electric price and gas price and calculate an effective MPG. It is not realistic to ignore the cost of electricity.
 

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That would be a good addition. In discussions you always end up having to explain the EPA ratings which use a energy equivalent vice a cost equivalent to calculate an effective mpg. Actual cost per mile is what consumers would care about. I have a hybrid furnace and it has the same issue in that I can program a crossover temperature for switching between Natural gas and heat pump but what I would really like is to be able to put the cost of each fuel in and let it manage the crossover based upon which is cheaper to use at a given temperature taking into account the efficiency of each heating method at that temperature.
 

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Some customers care most about cost per mile. Others care more about not burning gas, for environmental or national security reasons. I think any reason not to burn gas is a good reason. Of course, everyone cares how much money they are spending, but priorities can differ. The MPG display gives a direct comparison with gas-only cars. Most gasoline drivers don't know how much they are spending per mile. MPGe is a unit no one really understands. The amount of energy in a gallon of gasoline doesn't help to compare efficiency with a gas-only car, and it doesn't help figure out costs, either, because no one knows how much a kWh of gasoline costs or how much a gallon of electricity costs.

I like the MPG display, but I would like it to be capable of showing more than 250 mpg (I am at 319 mpg currently). Options are always good, though, so if it showed MPGe or something else in addition to what it shows now or had an option to show other units, that would be fine with me. I probably wouldn't use it, though.
 

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Displaying "Lifetime MPG" and MPG on the "A" and "B" displays is meaningless because it ignores the cost for electricity. MPGe is a term that is too confusing to understand and explain to people. It also cannot be compared to all electric cars (I don't think a Telsa will ever display MPGe).

It seems that the true common denominator is cents/mile, which can be calculated by the car by entering the per-gallon cost when one fills up and the cents/KWh that one typically pays. This would be problematic for people who charge at work for "free" (even though it isn't free to the company).

To replace the energy usage page, I would like a graph that shows the history of miles/KWh with an average since the last full charge and/or an average for some previous time period (week/month), even when running in charge sustaining mode. The car still is electric, right? In charge sustaining mode, it would be good to have a KWh/gallon graph, although I'm guessing that this isn't something that can be controlled by the way one drives.

I'd like to see the electric car industry agree on units - either miles/KWh or Wh/mile. I like the former because efficiency improves as the number gets bigger.
 

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Allow the driver to enter electric price and gas price and calculate an effective MPG. It is not realistic to ignore the cost of electricity.
Do you want MPGe or Cost per Mile? MPGe doesn't require knowing the cost of gas or electricity. It's purely a measurement of energy efficiency, cost is not part of the equation. An MPGe display would show: Total Miles Driven / (Gallons Burned + (kWh/33.7)).

Displaying "Lifetime MPG" and MPG on the "A" and "B" displays is meaningless because it ignores the cost for electricity. MPGe is a term that is too confusing to understand and explain to people. It also cannot be compared to all electric cars (I don't think a Telsa will ever display MPGe).

I'd like to see the electric car industry agree on units - either miles/KWh or Wh/mile. I like the former because efficiency improves as the number gets bigger.
MPGe can and is used to compare all electric cars and Tesla's do have an MPGe rating. That's the entire point, to enable normalized comparisons between vehicles using different fuel sources. The Tesla Model S-60 is rated at 95. The Volt is 98, and the Leaf is 115.

MPGe is essentially the same as miles/kWh, it's just miles/kWh*33.7. So 100MPGe is the same as 3miles/kWh. The EPA did perform focus group studies and found the general public found miles/kWh or kWh/100miles to be more confusing than MPGe because most folks don't understand a kWh. Read more at:
http://www.fueleconomy.gov/feg/label/learn-more-PHEV-label.shtml and
http://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalent

But if you were going to use a miles/kWh or Wh/mile or kWh/100mi and try to get the general public to make the switch, it would be better to use a consumption based figure rather than economy figure. IOW, use kWh/100miles rather than miles/kWh. Even though with miles/kWh the number gets bigger as efficiency improves, the problem is it's a non-linear relationship which makes it difficult to understand improvements from one vehicle to another - it's not intuitive. See the MPG illusion at http://www.mpgillusion.com/ which explains this problem well.

For example, using my numbers above, one might conclude that a Leaf which now gets 115MPGe is much better than the Volt which gets 98MPGe. After all, a 35MPG car is much better than a 20MPG car, right? The reality is 115MPGe vs. 98MPGe (or 3.4miles/kWh vs. 2.9miles/kWh if you prefer) is insignificant. If you take the inverse, it's 29kWh/100mi vs. 34kWh/100mi or about 60 cents worth of electricity. The advantage of the consumption based metric is it's linear so a difference of 5kWh/100mi is the same no matter what or likewise the difference of 5 GPM is constant.

No matter which way we measure it, it's going to take getting used to a new metric. Most people don't understand MPGe, true. But most also don't understand any of the kWh based metrics, nor is cost/mile meaningful. People might pay attention to what they pay per month in fuel, so for any cost based metric to have meaning it should show a monthly or yearly savings. When you're talking about saving a few pennies per mile, it just doesn't make an impact. Talk about saving hundreds or even thousands of dollars a year, now you get someone's attention.
 

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If you are concerned about cost, then the combined MPGe figure, including both gasoline and electricity, is not only confusing but useless. Depending on the driving pattern, there may be more gas and less electricity in that total or more electricity and less gas (especially in a Volt), and gallons of energy are not fungible in different forms. A gallon of gas does not cost the same as a gallon of electricity (or necessarily have the same environmental impact). That's why I don't like MPGe as a combined metric; it doesn't tell you anything. As a measurement of electric-only efficiency, MPGe at least tells you something if the efficiency of every electric car is displayed in the same units (as it is), but, as Joule Thief said, it tells you less than you think it does, because of its nonlinearity. Measuring electric energy in kWh instead of gallons would at least have the advantage of using a unit people associate with electricity already.
 

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If you are concerned about cost, then the combined MPGe figure, including both gasoline and electricity, is not only confusing but useless. Depending on the driving pattern, there may be more gas and less electricity in that total or more electricity and less gas (especially in a Volt), and gallons of energy are not fungible in different forms. A gallon of gas does not cost the same as a gallon of electricity (or necessarily have the same environmental impact). That's why I don't like MPGe as a combined metric; it doesn't tell you anything.
Yes and no. One could not assign a general combined (gas+elec) MPGe figure to all Volts because, as you say it's based on driving pattern and more specifically the EV%. But, if the vehicle displayed an MPGe number specific for that vehicle based on some given time period, then you could calculate your costs fairly accurately. First assume the Volt will on average get the same MPGe when driving all electric, and likewise will get the same average MPG when driving all gas. With that, any combined MPGe value is really nothing more than a different way of measuring EV% and a given MPGe number can only be achieved by driving a particular ratio of gas and electric.

For example, I recently ran my last 6 months of data. My actual MPGe in all electric was 106, and my MPG in gas mode was 40. If I were to create a model saying 106 correlates to 100% EV and 40 correlates to 0% EV, then for any MPGe value in between I can figure out almost exactly how much must have been electric and how much gas. I show that model below. In this case, my actual combined MPGe was 84 and my actual EV% was 84%. As you can see it fits perfectly with what I would have estimated my EV% to be if all I had was my MPGe number.

Volt MPGe vs EV%.jpg


EDIT: BTW my point is only that if your Volt could somehow tell you MPGe, it would correlate to some EV%. That said, it would be easier and more accurate to have the Volt just simply give you EV% since while the Volt IS capable of precisely measuring miles driven on gas and electric, it IS NOT apparently very good at estimating kWh used (as discussed in many other threads).
 

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I try and explain it to folks as such. The car runs on electricity. The electricity can come from either PG&E or gasoline. The car goes about 35 miles on $0.60 of electricity from PG&E or 35 miles on one gallon of gasoline for $4.00.
 

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It seems that the true common denominator is cents/mile, which can be calculated by the car by entering the per-gallon cost when one fills up and the cents/KWh that one typically pays.

I've spent the last 14 months trying to explain to other "villagers" where I live about the various reasons I bought a Volt and people here can't even figure out the "cents-per-mile" part (maybe all the villagers here are simpletons, I live in a rural region of Texas)...

I have to tell them, "When I go to the big city in my 4x4 in order to buy groceries and come all the way back to our village, it costs me about $30 in gasoline. If I go to the big city in my Volt, and come back, I am able to to that for about $2 in electricity." At this point, the villagers all start staring at each other and say "that thang runs on E-lek-trick?" And it just opens a big can of worms as I have to start explaining what an EV is, or a BEV and all the other various types. If I say "Hybrid" they ask, "You mean like crossin' a buffalo with a cow to make beefalo?"

I hope in by this time next year, I have moved back to the Big City where I can talk about kilowatt consumption and will have more confidence someone might have an inkling of what I am talking about.
 

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I've spent the last 14 months trying to explain to other "villagers" where I live about the various reasons I bought a Volt and people here can't even figure out the "cents-per-mile" part (maybe all the villagers here are simpletons, I live in a rural region of Texas)...
Most have little idea of what their cost per mile is. Most have a guess of what their MPG is. All know how much it costs to fill a tank and about how often they need to do it. Start talking MPGe and you might as well get the camera out and take pictures as their eyes roll into the back of their head and drool dribbles from the side of their mouth, haha.
 

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Most have little idea of what their cost per mile is. Most have a guess of what their MPG is. All know how much it costs to fill a tank and about how often they need to do it. Start talking MPGe and you might as well get the camera out and take pictures as their eyes roll into the back of their head and drool dribbles from the side of their mouth, haha.

You are correct, sir....

Being the son of a pilot and a pilot myself, I've spent a good part of my life figuring out fuel consumption/endurance/range/headwinds... (I mean, you run outta gas in an airplane... you can't pull into a Walmart and buy gas...) and some people out here only figure "it takes 1/2 my paycheck each month to buy gas..." I guess that is what I get, for trying to convenience the head cook at our Dairy Queen, how little a Volt costs to operate.

For me, owning a Volt is the highlight of my times of driving a car. But at the same time, owning a Volt and trying to explain it to people at the local coffee shop, is one of the larger frustrations in life.

I probably should consider moving to Palo Alto, but folks there might not appreciate me having chickens and goats and a burro in the front yard.
 

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First assume the Volt will on average get the same MPGe when driving all electric, and likewise will get the same average MPG when driving all gas. With that, any combined MPGe value is really nothing more than a different way of measuring EV% and a given MPGe number can only be achieved by driving a particular ratio of gas and electric.
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BTW my point is only that if your Volt could somehow tell you MPGe, it would correlate to some EV%. That said, it would be easier and more accurate to have the Volt just simply give you EV% since while the Volt IS capable of precisely measuring miles driven on gas and electric, it IS NOT apparently very good at estimating kWh used (as discussed in many other threads).
Combined MPGe would be a bad estimate of EV%, since people can get different electric efficiency and different MPG on different days, depending on how and where they drive and what the weather is like. Certainly, someone isn't going to look at the MPGe on the display and figure out their EV% and how much it costs to drive in their heads. With a pocket calculator they could come up with a guess, but what would be the point? Myvolt.com tells you total miles driven, electric miles driven, gas miles driven, kWh used (not sure whether it is from the battery or taken in through the charge port), and gallons used. That gives you enough to approximate whatever you want as a big picture, and how many cents one trip costs isn't very important.

I don't think there is any way to measure the Volt's energy usage exactly without taking some kind of measurements every day and keeping a log by hand (maybe there are some electric meters that will do this if the Volt is the only thing on the meter), and not many are going to care enough to do all that work. A configurable display is good, because it makes more people happy, especially if they can put in relevant parameters to get actual cost per mile, per month, per year, or whatever they find useful, but combined MPGe would just be a number that looks good, but doesn't tell you much. It tells you that electric motors convert energy to motion more efficiently than gas engines do, but it is enough to learn that once and never look at the MPGe number again.
 

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If you try to get cost per mile, getting free charging throws another monkey wrench into the equation.
 

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That would be a good addition. In discussions you always end up having to explain the EPA ratings which use a energy equivalent vice a cost equivalent to calculate an effective mpg. Actual cost per mile is what consumers would care about. I have a hybrid furnace and it has the same issue in that I can program a crossover temperature for switching between Natural gas and heat pump but what I would really like is to be able to put the cost of each fuel in and let it manage the crossover based upon which is cheaper to use at a given temperature taking into account the efficiency of each heating method at that temperature.
I use the same dual-fuel setup in the house. Of course if the system calculated the switchover temp from costs, then you would have to feed it real-time cost data. And we wonder why SW expands to fill available memory & processor cycles.
 

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I probably should consider moving to Palo Alto, but folks there might not appreciate me having chickens and goats and a burro in the front yard.
East Palo Alto maybe? (Closer to the bay.)
 

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Combined MPGe would be a bad estimate of EV%, since people can get different electric efficiency and different MPG on different days, depending on how and where they drive and what the weather is like.

I don't think there is any way to measure the Volt's energy usage exactly without taking some kind of measurements every day and keeping a log by hand (maybe there are some electric meters that will do this if the Volt is the only thing on the meter)
Yes I agree, and I wasn't suggesting MPGe is a good method for driving a cost calculation. I was only saying it is possible to do, and I don't think it would be a bad estimate. It wouldn't be perfect either, but even accounting for the 3Ts, I think you could get within 5% of actual.

If the primary goal is understanding your cost to drive, then yes MPGe doesn't answer that question very well (at least not without doing a bunch of additional calcs). But from an engineering efficiency perspective, if you are trying to compare vehicles of varying fuel types to determine which one is most efficient at driving a certain distance on a given amount of energy, then MPGe works well. Of course most people don't really care about that.

The MyVolt.com kWh tracking is useless and unreliable. AFAIK it's based on the same algorithm as the display inside the car which only estimates kWh used, it's not an actual measurement. So, as you say, the only good way to get accurate kWh usage is to have a dedicated power meter. Some folks have their EVSE's at home on dedicated meters (in Cali you get special rates on PGE's TOU E9B plan by doing this). I have a Blink EVSE which monitors the power to my Volt and keeps a log which I can download online. That's what I use to calculate my actual MPGe, kWh/mi, etc.

But in general I agree that displaying MPGe inside the vehicle will have limited value to most folks. I wouldn't mind having it as an option, but only if the Volt could accurately track kWh usage, which currently it can't.

I suppose if what people really want is some kind of cost to drive display (like the configurable display you describe), that could be useful. But that would still have limitations. To start with, gas prices fluctuate daily. And electric rates can vary by time of day, day of week, season (summer/winter), etc. On top of that if you do any public or workplace charging, that could throw it off too. And then we're still left with the reality that the Volt simply can't keep a good count of kWh, so I'm afraid folks are going to be stuck with using MyVolt.com, VoltStats.net, their power meters, and that pocket calculator :)
 

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If the primary goal is understanding your cost to drive, then yes MPGe doesn't answer that question very well (at least not without doing a bunch of additional calcs). But from an engineering efficiency perspective, if you are trying to compare vehicles of varying fuel types to determine which one is most efficient at driving a certain distance on a given amount of energy, then MPGe works well. Of course most people don't really care about that.
I agree on all counts. MPGe is OK for engineers, not so useful for the common man (or woman). QED. :)
 

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If you're on a Time-Of-Use plan like I am, how do you figure the cost if I come home and do a partial charge of a couple of kWh during peak hours, use up some of the battery, then go home and charge back to full during super off peak rates?

I absolutely hate "MPGe". They should've called it something else like EDE (Electrical Drivetrain Efficiency). Anything without the commonly used "MPG" acronym in it.
 

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Allow the driver to enter electric price and gas price and calculate an effective MPG. It is not realistic to ignore the cost of electricity.
+1 Exactly. (Prius lets you input the gas price and a reference mpg to get comparison and savings.)

The MPG is at best misleading and basically useless to me. Sure, it may be technically correct (or maybe not) but it's just wrong to say xxx mpg when most of those miles didn't require any gas. If you do not use any gas, there are 0 miles per gallon - or is it infinite mpg? But if you use a very little now you're at hundreds of miles per gallon... I'm a "marketing guy" and I expect this display was not created by an engineer.

It would not be difficult to offer multiple options to personalize this screen. I imagine for most of us the large sphere on the left is useless as well, since most will charge fully at some point each day/night.

There should be options to see lifetime percentages, gallons used, kwh used, fuel saved, etc. And let me see those same metrics for Trip A and B. Why is it just from the beginning of time (lifetime) or "this charge" - also useless. Same with the efficiency calcs.

With the amount of work that went into everything about the car, this piece is so poorly done it seems like an afterthought. Or they gave it to the marketing team to make it look impressive rather than be useful... (says the marketing guy...)
 
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