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Like many on the forums, while waiting for M3D delivery I'm reading and learning. One puzzling question keeps coming to mind after seeing numerous posts referring to the "wh/mile" metric. It seems backwards.

ICE vehicles have used MPG (miles per gallon) as the fuel efficiency metric for as long as I can remember. Miles is the travel distance and a gallon of gas or diesel is the fuel metric.

Just curious as to why folks are flipping the numbers around with EVs, i.e. using fuel as the numerator and travel distance as the denominator. I'm assuming there is a good reason why and would like to better understand.

What is the some underlying reasoning here? Wouldn't it make more sense for the EV market to stick to a fuel efficiency calculation everyone already understands?

For example, let's say the average M3 with the long range battery (with roughly 70 KWH usable capacity) can drive roughly 300 miles between charges. This would equate to a "fuel" efficiency rating of roughly 4.2 miles per KWH, right? Why would the market not use this more simple terminology rather than wh/mi?

ICE vehicles have used MPG (miles per gallon) as the fuel efficiency metric for as long as I can remember. Miles is the travel distance and a gallon of gas or diesel is the fuel metric.

Just curious as to why folks are flipping the numbers around with EVs, i.e. using fuel as the numerator and travel distance as the denominator. I'm assuming there is a good reason why and would like to better understand.

What is the some underlying reasoning here? Wouldn't it make more sense for the EV market to stick to a fuel efficiency calculation everyone already understands?

For example, let's say the average M3 with the long range battery (with roughly 70 KWH usable capacity) can drive roughly 300 miles between charges. This would equate to a "fuel" efficiency rating of roughly 4.2 miles per KWH, right? Why would the market not use this more simple terminology rather than wh/mi?

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## Comments

But Tesla has chosen to present wh/mile, so that is what going to be mostly discussed in these forum.

There--fixed that for ya. You've got the U.S.-centric blinders on. All of the countries that use the metric system use the inverse number of liters per 100km for their efficiency rating, which is a fuel consumption number, just like watt hours per mile.

When people think of efficiency they are more likely to become more efficient drivers. And that is better for us all. And the environment.

The bolt. eGolf. Fiat. All show it in mi/kw.

At 260 kw per 100 and a 310 mile range (310 * 0.26 = 80.6 kwh battery) but that is not right. So... what gives on these numbers? Anyone know?

It's been hard for me to achieve 242 Wh/mi unless I use Chill mode.

Second, Wh/km is the “correct” measure. @ravisundaramam “ I think Bolt and Leaf use miles/kWh” - nope, at least not in the LEAF. It measures and displays Wh/km. Well actually it displays kWh/km which is less useful, since my LEAF does 0.14 kWh/km which is far less user friendly than 140 Wh/km.

Finally, the nice thing about Wh/km is that your goal is to get that number as close to zero as possible instead of as close to infinity as possible.

It makes sense to you because that’s what you’re used to. In ten years of driving a Tesla your opinion may change.

260 kw per 100? Did you mean 260 kwh/100 mi? If so, that is a horrendous driving efficiency. That would be 2,600 wh/mi. Or a range of about 29 miles per full charge.

310 miles is an estimated range. 75 kwh is the actual battery capacity. Your driving efficiency determines your actual range. If you are getting an efficiency of 2600 wh/mi on a 75 kwh battery your range would be 28.8 miles.

To get the rated range of 310 miles you would need an efficiency of about 242 wh/mi (24.2 kwh/100 mi)

If the metric is mi/kwh the number is too small to use to adjust one’s driving to become more efficient. Unless it is stated to several decimal places it doesn’t change fast enough.

Wh/mi metric is a much nicer feedback if your goal is efficiency.

Into the future we go!

Wrong—Japan uses kpl—km/lt—kilometers per meter, known as ねんぴ (nempi). Fixed that for ya...

EPA figure is based on efficiency from the wall, not the battery, so there are frictional losses of charging included as well.

What is important in this kind of thing is your reference point. That is how we gain understanding/insight into what the numbers are telling us. Some of us will have to gain a new reference point as we get accustomed to a new unit of measure. It won't be better or worse, it will just be different.