Calculating MPGe

[Jasper7821]

I'm just curious what the MPGe is for my FFE.
The EPA standard is 33.7kw equal 1 gallon of gas.
But wouldn't that be different wherever you live and what gas and electric prices are.
In Tucson the gas rates don't change from day to night, they only change from winter to summer and it's only a tiny change.
Regular gas here is about 3.2 and my electricity without adding 20% for efficiency is 8 cents per kw.
So I divide $3.2 by $.08 and get 40. So wouldn't my MPGe be based on 40kw equals a gallon of gas.

My work commute yesterday to work was 203wh/mile so wouldn't that be 197MPGe ?
my commute home was 312wh/mile which was 128MPGe
And the daily avg. was 257wh/mile which equals 156MPGe.

I divided 40,000 by the wh/mile.

I totally sucked in math and it's all getting confusing but is this the way to calculate my MPGe ?

EDIT,
recalculated with the 33.7 EPA standard
going to work 166MPGe
going home 108MPGe
daily work commute avg. 131MPGe

 

[DavidJohnson]

I just calculated mine the other day and this how I did it. I was only interested in the overall MPGe since I got the car about 3 months ago. The formula I found is shown below. I found my lifetime energy usage on the dash info (lefthand side) when I turned the car off. My data was: 1) 1300 miles, 2) average energy rate was 316 wh/mi.

MPGe = 32,600 / Ave (displayed in wh/mi)
MPGe = 32,600 / 316
MPGe = 103

So, I'm getting 103 MPGe for my combined city and highway driving. Right in line with what I would expect. Hope this helps!

 

[WattsUp]

Jasper, the 33.7 kWh per gallon equivalency (from the EPA) assumes an ~80% charging efficiency, if that helps you. Again, this is because all the numbers they report are attempting to equate "buying energy from a wall socket" with "buying gas from a pump".

David, where does your "32,600" number come from?

 

[Jasper7821]

I just calculated mine the other day and this how I did it. I was only interested in the overall MPGe since I got the car about 3 months ago. The formula I found is shown below. I found my lifetime energy usage on the dash info (lefthand side) when I turned the car off. My data was: 1) 1300 miles, 2) average energy rate was 316 wh/mi.

MPGe = 32,600 / Ave (displayed in wh/mi)
MPGe = 32,600 / 316
MPGe = 103

So, I'm getting 103 MPGe for my combined city and highway driving. Right in line with what I would expect. Hope this helps!

I've only had my car for 2 days now and it sat at the dealer for 7 months and the lifetime has gone down a bit but it's at 344wh/mile so I can't use that number.
I wish I could reset it somehow. But it's good that after a few years someone can look at that and tell how the car was driven if someone was buying a used one.

 

[Jasper7821]

Jasper, the 33.7 kWh per gallon equivalency (from the EPA) assumes an ~80% charging efficiency, if that helps you. Again, because all the numbers the report are attempting to equate "buying energy from a wall socket" with "buying gas from a pump".

David, where does your "32,600" number come from?

Ahh, I already forgot that you told me that before. So sorry.
recalculated and edited my first post.

 

[jmueller065]

You can reset the lifetime summary data. It's on the menu on the left screen on the dash.

 

[Jasper7821]

You can reset the lifetime summary data. It's on the menu on the left screen on the dash.

Ok, cool. Thanks
I went threw the settings menu on the left screen and didnt see it.
I'll go thew again and reset it.
Thanks again

 

[WattsUp]

EDIT,
recalculated with the 33.7 EPA standard
going to work 166MPGe
going home 108MPGe
daily work commute avg. 131MPGe

Well, your numbers are still not quite right. You didn't account for the charging efficiency in the proper way just yet.

The 33.7 kWh/gallon gasoline equivalency given by the EPA is relative to the total energy required to charge an EV. In other words, the 33.7 kWh/gallon figure includes the energy "wasted" during charging (which, as we've discussed, is about 20%). We'll call this 20% the "charging overhead". The Wh/mile reported by the car, on the other hand, excludes the charging overhead because it measures only what the car internally draws from its battery. And the battery obviously holds only the energy left after charging is complete. The charging overhead is not reflected in the Wh/mile reported by the car.

Here's the important consequence to realize: You cannot use the Wh/mile numbers reported by the car to directly divide the EPA's gasoline equivalency. You must first include the charging overhead. This is where a lot of people get confused and end up computing inflated MPGe and other numbers (usually all 20% inflated).

To compute your MPGe correctly, you must add the charging overhead back to the Wh/mile numbers reported by the car. This will give you the total energy that ultimately came out of the wall and enabled the car to drive a distance of one mile. It is this total amount of energy per mile that can be correctly used with the EPA gasoline equivalency.

So, assuming the typical charging overhead of 20% (aka, charging efficiency of 80%), the computation for the total energy used during your commute is easy:

Going to work: 203 Wh/mile (reported by car) / 0.8 (charging efficiency) = 253 Wh/mile (total energy)
Coming back home: 312 Wh/mile (reported by car) / 0.8 (charging efficiency) = 390 Wh/mile (total energy)

These total energy numbers allow us to compute your MPGe:

33.7 kWh/gallon / 253 Wh/mile = 133 MPGe
33.7 kWh/gallon / 390 Wh/mile = 86 MPGe

And finally, we get the average for your overall commute:

((253 + 390) / 2) = 321 Wh/mile, or equivalently, 105 MPGe

Look at that... you're the perfect typical FFE driver! You're getting exactly the MPGe advertised by Ford.

 

[WattsUp]

I just calculated mine the other day and this how I did it. I was only interested in the overall MPGe since I got the car about 3 months ago. The formula I found is shown below. I found my lifetime energy usage on the dash info (lefthand side) when I turned the car off. My data was: 1) 1300 miles, 2) average energy rate was 316 wh/mi.

MPGe = 32,600 / Ave (displayed in wh/mi)
MPGe = 32,600 / 316
MPGe = 103

So, I'm getting 103 MPGe for my combined city and highway driving. Right in line with what I would expect. Hope this helps!

David, something seems not quite right with your numbers. I don't think you've accounted for charging efficiency. The car only reports the energy it consumed internally from its battery, but this is not the same as the total energy that was required externally to charge the battery. MPGe is computed using the total external energy.

To get specific with your example, if the average Wh/mile reported internally by your FFE is 316 Wh/mile, then your total external energy usage was 395 Wh/mile on average, assuming the typical charging efficiency of 80%:

316 Wh/mile (reported by car) / 0.8 (charging efficiency) = 395 Wh/mile (external energy)

It is only this total external energy (the energy you ultimately "supplied to" the car while charging it), per mile driven, that can be used with the EPA gasoline equivalency of 33.7 kWh/gallon, in order to correctly compute MPGe:

33.7 kWh/gallon / 395 Wh/mile = 85 MPGe

So, you've been getting 85 MPGe over the lifetime of your FFE so far, not 103. I would also guess that you typically see an expected range of around 60-65 miles on a full charge?

19.5 kWh (usable battery capacity) / 316 Wh/mile (internally used by car) = 62 miles

------

To get the expected 105 MPGe advertised by Ford for the FFE, you need to maintain an average internal energy use of 256 Wh/mile (as displayed by the car). Externally, this translates into 320 Wh/mile total energy required (assuming 80% charging efficiency). And this is precisely how the EPA arrived at their estimate of 105 MPGe for the FFE:

33.7 kWh/gallon / 320 Wh/mile (external energy) = 105 MPGe

Further, we can see that 105 MPGe translates directly into the expected range of 76 miles, keeping in mind the usable battery capacity of the FFE:

19.5 kWh (usable battery capacity) / 256 Wh/mile (internally used by car) = 76 miles

------

My personal lifetime energy usage is 265 Wh/mile, or 101 MPGe:



265 Wh/mile / 0.8 (charging efficiency) = 331 Wh/mile
33.7 kWh/gallon / 331 Wh/mile = 101 MPGe

I would stay my typical range on a full charge is 70-75 miles, which is borne-out by the numbers:

19.5 kWh / 265 Wh/mile = 73 miles

And since my range is typically slightly less than the nominal 76 mile range, it makes sense that my MPGe is slightly less than 105 MPGe.

 

[Jasper7821]

EDIT,
recalculated with the 33.7 EPA standard
going to work 166MPGe
going home 108MPGe
daily work commute avg. 131MPGe

Well, your numbers are still not quite right. You didn't account for the charging efficiency in the proper way just yet.

The 33.7 kWh/gallon gasoline equivalency given by the EPA is relative to the total energy required to charge an EV. In other words, the 33.7 kWh/gallon figure includes the energy "wasted" during charging (which, as we've discussed, is about 20%). We'll call this 20% the "charging overhead". The Wh/mile reported by the car, on the other hand, excludes the charging overhead because it measures only what the car internally draws from its battery. And the battery obviously holds only the energy left after charging is complete. The charging overhead is not reflected in the Wh/mile reported by the car.

Here's the important consequence to realize: You cannot use the Wh/mile numbers reported by the car to directly divide the EPA's gasoline equivalency. You must first include the charging overhead. This is where a lot of people get confused and end up computing inflated MPGe and other numbers (usually all 20% inflated).

To compute your MPGe correctly, you must add the charging overhead back to the Wh/mile numbers reported by the car. This will give you the total energy that ultimately came out of the wall and enabled the car to drive a distance of one mile. It is this total amount of energy per mile that can be correctly used with the EPA gasoline equivalency.

So, assuming the typical charging overhead of 20% (aka, charging efficiency of 80%), the computation for the total energy used during your commute is easy:

Going to work: 203 Wh/mile (reported by car) / 0.8 (charging efficiency) = 253 Wh/mile (total energy)
Coming back home: 312 Wh/mile (reported by car) / 0.8 (charging efficiency) = 390 Wh/mile (total energy)

These total energy numbers allow us to compute your MPGe:

33.7 kWh/gallon / 253 Wh/mile = 133 MPGe
33.7 kWh/gallon / 390 Wh/mile = 86 MPGe

And finally, we get the average for your overall commute:

((253 + 390) / 2) = 321 Wh/mile, or equivalently, 105 MPGe

Look at that... you're the perfect typical FFE driver! You're getting exactly the MPGe advertised by Ford.

Ahhh, ok. I see (kinda, now it's late and a a few drinks and its not making sense.
If I already deducted 20% of the 40kw's and got the 33.7 then wouldn't my numbers already have the 20% deducted and whatever the car said then that's what it is.
I'll re-read tomorrow and I'm sure I'll get it.
Thanks

 

[Jasper7821]

One more question.
What does miles to regen mean on the trip summary?

 

[WattsUp]

If I already deducted 20% of the 40kw's and got the 33.7 then wouldn't my numbers already have the 20% deducted and whatever the car said then that's what it is.

Hmm, no. I'm not sure where you got the number 40 from. You don't need to deduct anything from the 33.7 kWh/gallon equivalency figure. It already accounts for the typical EV charging efficiency.

Also note that the 33.7 kWh/gallon figure represents energy equivalency only. It has nothing to do with price (which I think you were sort of asking about this in your very first post in this thread). The cost of gas or electricity can change, and the 33.7 kWh equivalency will remain.

The EPA is simply saying that, purely from an energy usage perspective, if you obtain 33.7 kWh from your electric utility, and supply it to your EV through a charging process (with the typical 80% efficiency), it is equivalent to obtaining a gallon of gasoline from your local service station, and putting it in your ICE. If both vehicles are then able to drive the same distance (before consuming all their energy), each would receive the same "MPGe" rating.

As we know, however, EVs can go much further on 33.7 kWh than ICE-mobiles can go on a gallon of gasoline (because converting electricity into mechanical motion is much more efficient than doing the same with gasoline), and so have much higher MPGe ratings.

To reiterate, 1 gallon of gas and 33.7 kWh of electricity might each cost different amounts of money (and, in fact, they do), but this does not affect the MPGe rating. The fact that EVs are both much more efficient machines, and electricity also much cheaper than gas, is a big part of what makes EVs so attractive financially (in the long run).

--------

Btw, "MPG equivalency", or MPGe, is simply a way for people used to ICE vehicles and "miles-per-gallon" ratings to evaluate the performance of EVs compared to their gasoline-powered counterparts. But, ultimately, people care about cost, not some conceptual energy equivalency.

Since the cost of gasoline and electricity are so different (currently, electricity is much cheaper, for the same amount of energy), an MPGe rating on an EV really doesn't tell you much in terms of economy, only efficiency. An MPGe of 100? So what. I can't use the current price of gas to figure out how much the EV will cost to operate. Why? Because the prices of gas and electricity are unrelated. Instead, I'll need to convert 100 MPGe back into the equivalent kWh/mile (which, for 100 MPGe, is 337 Wh/mile), and find out what my electric utility is charging per kWh.

IMO, as a conceptual exercise, MPGe ratings "perhaps" provide a familiar way to compare the efficiency of an EV to the efficiency of an ICE vehicle. But, if you're comparing only EVs, then Wh/mile would make a much more direct comparison.

 

[WattsUp]

One more question.
What does miles to regen mean on the trip summary?

You mean the "miles from regen" number? This number provides an estimate of how many "extra" miles of range were added purely due to energy captured from regeneration (and stored in the battery).

Keep in mind that an "electric motor" and an "electric generator" are the same physical device. When you apply electric current, the device produces mechanical motion. When you apply mechanical motion, it produces electric current. Whenever an EV is doing the latter (which also functions to slow the car down) we call it "regeneration".

Regeneration is one of reasons EVs are so efficient. Instead of wasting energy when slowing down, they recapture some of it. With an ICE, once you've gained speed through burning gasoline, there is no way to ever get that energy back. You can't convert any of the resulting mechanical motion (the forward momentum of the car) back into gasoline. With an EV, you can.

 

[Jasper7821]

One more question.
What does miles to regen mean on the trip summary?

You mean the "miles from regen" number? This number provides an estimate of how many "extra" miles of range were added purely due to energy captured from regeneration (and stored in the battery).

Keep in mind that an "electric motor" and an "electric generator" are the same physical device. When you apply electric current, the device produces mechanical motion. When you apply mechanical motion, it produces electric current. Whenever an EV is doing the latter (which also functions to slow the car down) we call it "regeneration".

Regeneration is one of reasons EVs are so efficient. Instead of wasting energy when slowing down, they recapture some of it. With an ICE, once you've gained speed through burning gasoline, there is no way to ever get that energy back. You can't convert any of the resulting mechanical motion (the forward momentum of the car) back into gasoline. With an EV, you can.

Got it all, thank you very much.
And the final question, does coasting regenerate anything. Is it better to go fairly quick from the gas to the brake when approaching a red light in the distance. It seems I'm trying to get on the brakes pretty quick after letting the car coast for just a bit as it see the spinning arrow only on braking and not coasting.
Whatever I'm doing it seems pretty efficient as I've only had the car less than a week and I'm already on some of the stat top tens.

 

[WattsUp]

And the final question, does coasting regenerate anything. Is it better to go fairly quick from the gas to the brake when approaching a red light in the distance. It seems I'm trying to get on the brakes pretty quick after letting the car coast for just a bit as it see the spinning arrow only on braking and not coasting.
Whatever I'm doing it seems pretty efficient as I've only had the car less than a week and I'm already on some of the stat top tens.

Yes, regeneration occurs when coasting. Indeed, regen occurs anytime the car is not "driving" the motor (and discharging the battery). During those times, the motor (working like a generator) is, if you will, "driving" the battery instead (recharging it). This process creates mechanical resistance at the wheels which, if purposely manipulated, can be used to slow the car down in a controlled manner.

In practice, the computer actually balances the flow of electricity to the motor, purposely modulating the level of resistance (otherwise the effect would be quite severe and the car would slow down very suddenly when taking your foot off the accelerator). One of the inputs to the computer's modulation algorithm is the brake pedal. The more you press, the more resistance is added, and the more the car slows. In this way, as EV drivers, it is possible to use motor resistance for much of our "braking", while at the same time benefiting from the resulting regen. It is only when motor resistance alone cannot slow the car enough that your FFE will apply its mechanical brakes to assist.

Btw, in the 3.1 software, for whatever reason, Ford decided to display the "regen" animation only during braking. In reality, the FFE is programmed to also perform "just a bit" of regen when coasting in D, and a "bit more" when coasting in L. Note that the D and L settings on the "gear shift" are not actual gears like in an ICE, they are merely different levels of motor resistance. (Heck, even R isn't a real gear in the FFE; to move backwards, the polarity of the current being supplied to the motor is simply reversed, which of course turns the wheels in the opposite direction.)

In the upcoming 3.5 software, supposedly the regen animation appears whenever the car is regenerating. (This is what I've heard from others here in the forum who already have the new software.) This would mean, I presume, that the animation appears whenever you take your foot off the accelerator, in addition to when braking. But, even though the animation only shows during braking with the 3.1 software, rest assured that your FFE, no matter what software version you have, is indeed regenerating while coasting.

So, when coming up to a stop, you can simply take your foot off the accelerator and begin to slow while coasting for a period. Then, brake normally as you get closer. Well, depending on what kind of driver you are... You may already brake "gently", but if you're a "rough" driver, you may want to practice becoming more "mellow", so as to get the most out of regen. This is what the "Brake Coach" scores in the FFE help you learn to do. When you score 100%, it means you used motor resistance exclusively to come to a full stop (and thus got the maximum possible regen). But, you can only achieve a score of 100% if you slow down gradually enough.

Thanks for all the good questions, Jasper!

 

[Jasper7821]

And the final question, does coasting regenerate anything. Is it better to go fairly quick from the gas to the brake when approaching a red light in the distance. It seems I'm trying to get on the brakes pretty quick after letting the car coast for just a bit as it see the spinning arrow only on braking and not coasting.
Whatever I'm doing it seems pretty efficient as I've only had the car less than a week and I'm already on some of the stat top tens.

Yes, regeneration occurs when coasting. Indeed, regen occurs anytime the car is not "driving" the motor (and discharging the battery). During those times, the motor (working like a generator) is, if you will, "driving" the battery instead (recharging it). This process creates mechanical resistance at the wheels which, if purposely manipulated, can be used to slow the car down in a controlled manner.

In practice, the computer actually balances the flow of electricity to the motor, purposely modulating the level of resistance (otherwise the effect would be quite severe and the car would slow down very suddenly when taking your foot off the accelerator). One of the inputs to the computer's modulation algorithm is the brake pedal. The more you press, the more resistance is added, and the more the car slows. In this way, as EV drivers, it is possible to use motor resistance for much of our "braking", while at the same time benefiting from the resulting regen. It is only when motor resistance alone cannot slow the car enough that your FFE will apply its mechanical brakes to assist.

Btw, in the 3.1 software, for whatever reason, Ford decided to display the "regen" animation only during braking. In reality, the FFE is programmed to also perform "just a bit" of regen when coasting in D, and a "bit more" when coasting in L. Note that the D and L settings on the "gear shift" are not actual gears like in an ICE, they are merely different levels of motor resistance. (Hack, even R isn't a real gear in the FFE; to move backwards, the polarity of the current being supplied to the motor is simply reversed, which of course turns the wheels in the opposite direction.)

In the upcoming 3.5 software, supposedly the regen animation appears whenever the car is regenerating. (This is what I've heard from others here in the forum who already have the new software.) This would mean, I presume, that the animation appears whenever you take your foot off the accelerator, in addition to when braking. But, even though the animation only shows during braking with the 3.1 software, rest assured that your FFE, no matter what software version you have, is indeed regenerating while coasting.

So, when coming up to a stop, you can simply take your foot off the accelerator and begin to slow while coasting for a period. Then, brake normally as you get closer. Well, depending on what kind of driver you are... You may already brake "gently", but if you're a "rough" driver, you may want to practice becoming more "mellow", so as to get the most out of regen. This is what the "Brake Coach" scores in the FFE help you learn to do. When you score 100%, it means you used motor resistance exclusively to come to a full stop (and thus got the maximum possible regen). But, you can only achieve a score of 100% if you slow down gradually enough.

Thanks for all the good questions, Jasper!

Cool, thank you very much. Now I can let off the gas sooner knowing that coasting will regen.
BTW, I'm a pretty good at braking I most always get 100%.
I'm getting awesome range results and every time I charge he range goes up.
I have have one more hour left to charge and its at 86% and range of 89 miles.

 

[jmueller065]

In the upcoming 3.5 software, supposedly the regen animation appears whenever the car is regenerating

Yes this is the case in my FFE. Simply lifting your foot off the accelerator causes the regen animation to appear.

 

[Jasper7821]

In the upcoming 3.5 software, supposedly the regen animation appears whenever the car is regenerating

Yes this is the case in my FFE. Simply lifting your foot off the accelerator causes the regen animation to appear.

Ddo you knkw that software can load automatically, or manually do it through the touch screen, or have to be taken in to the dealer?

 

[v_traveller]

I've only had the car less than a week and I'm already on some of the stat top tens.

If you're looking for some competition, try checking out the Region 1 stats.

 

[jmueller065]

Ddo you knkw that software can load automatically, or manually do it through the touch screen, or have to be taken in to the dealer?

Some My Ford Touch updates can be done via the syncmyride.com website. For this one, I suspect, that it must be done by the dealer due to the fact that the dash software also needs updating (The dash can only be updated by the dealer).

As far as I know the car can't update via its internal network connection.